Who would buy a football club? The question is as pertinent as the joke about the only way to walk away from an investment in the game with £10m being to start out with 10 times that figure.

Rangers' commercial horizons were grim enough – owing to a relatively small television deal and the removal of automatic Champions League qualification – without the potentially ruinous tax tribunal which hung over the club at the time of Craig Whyte's takeover, last May. As Rangers slipped into administration earlier this week, the most damning indictment of Whyte is that the alleged non-payment of around £9m to Her Majesty's Revenue and Customs was the trigger. It is Whyte's running of Rangers, rather than what went on before, which is rightly under sharp focus.

The key intrigue about Whyte is as relevant now as it was nine months ago: why would any businessman step forward to take over a company facing a contingent liability of £36.5m plus penalties, which it would clearly have struggled to absorb?

Whyte's explanations of his motives have always been as unconvincing as his attempts at providing background into his own business dealings. Asked why he bought Rangers, Whyte would only ever point out that he was a fan and that "nobody else stepped up to the plate".

He has been reluctant to explain anything about his business life. Last September, when meeting the Scottish press, he was asked to offer just a single example of a company which he had successfully turned around from a difficult position. The 41-year-old declined on the grounds he likes to keep his affairs private.

Again in a statement on Friday, Whyte said: "I knew when I stepped up to take over the club that the challenge of restoring Rangers to financial health after many years of living well beyond its means would be daunting. But I accepted it, both as a life-long Rangers fan and as a businessman with experience in turning round companies in distress." Included in that address was typical lambasting of "ill-informed" and "malicious" press reporting.

Duff & Phelps is the administrator now in charge of Rangers. A partner in that company, David Grier, was all smiles when taking adulation alongside Whyte at Ibrox last May. Nine months on, administrators went to great lengths to publicly stress there should be no suggestion of a conflict of interests and that such an arrangement was perfectly normal. At the very least, it should be clarified exactly what consultancy advice to Rangers Grier was involved in around the time of the buyout.

When the BBC aired a documentary which shone a light on to his business life, Whyte banned the broadcaster from Ibrox and promised legal action. On Friday the BBC confirmed it had received a libel writ from Whyte's lawyers.

Presiding over one of the biggest institutions in British sport was never likely to offer Whyte the anonymity he supposedly craves. His arrival on the scene to buy out Sir David Murray's 85% stake in Rangers through a firm named Wavetower – for £1, as it later transpired – was also met with scepticism by members of the club's board.

Those directors had one basic fear: that Whyte lacked the resource to fund Rangers to an appropriate level. Yet attempts to block the takeover were almost impossible due to Lloyds bank's desire to remove Rangers from both Murray's control and its own debtor list.

Alastair Johnston, the Rangers chairman at the time of the purchase, has been vociferous in his criticism of Whyte. Johnston has also requested that the takeover be investigated by both the police and the government's insolvency service.

It is known that Whyte served a seven-year ban as a company director from 2000. The Scottish FA belatedly investigated whether his arrival as the Rangers chairman in 2011 contravened its fit and proper person criteria and on Friday announced a "full and independent inquiry into the activities of Rangers FC and, specifically, a number of potential breaches of the Scottish FA's Articles of Association".

The SFA added that its effort to investigate Whyte under the fit and proper person rule "has been restricted by the club's solicitors' continued failure to share information in a timely or detailed manner". Which, naturally, begs the question as to whether any level of regulatory scrutiny by the football authorities was applied in the first place.

Johnston's theory has long been clear: that Whyte is a hedge fund player who gambled on Rangers both winning and losing the tax tribunal. In either case, Whyte believed he could sell on a "clean" company for at worst a small profit. If Rangers won the tax case, the club could have been sold on clear of the liability.

Losing it would always have meant administration and with HMRC forced to accept a reduced payment under a company voluntary agreement, Whyte's status as a secured creditor – obtained by buying out an £18m debt owed to Lloyds bank by Rangers, which remains as a liability to one of his other companies – meant any new buyer would be obliged to pay him back, with interest. "We could tell from the tiny amount of due diligence he carried out on cash flow, for example, that this wasn't to be a long-term project," Johnston said.

Two key events could have hampered Whyte's plan. The tax tribunal, initially to be heard last May, was postponed until November and then January. The outcome has yet to be announced. Furthermore, Rangers' failure to qualify for the group phase of either the Champions League or Europa League would have had an impact on revenue streams. What monies, therefore, have been used to fund Rangers during these intervening months?

Whyte sold four year's worth of season ticket sales for £24.4m to Ticketus, a London-based investment company, thereby mortgaging Rangers' main source of income. He denies part of that money was used to repay Lloyds. Rangers' administrators conceded on Thursday they are investigating where and how the Ticketus funds were actually used.

The non-publication of Rangers' accounts for the financial year to 30 June 2011 only adds to the lack of clarity regarding the takeover. Whyte claims to have provided £33m of his own money to clear the club's bank debts and fund the takeover. When proof of funds to buy the club was shown via a bank account belonging to Whyte's solicitors on 7 April last year there was just over £27m in place. Whether coincidence or not, that adds up almost exactly to the total of the bank debt, a promised £5m transfer kitty for the Rangers manager, Ally McCoist, another £2.8m tax payment due to HMRC and the £1.7m required for Ibrox infrastructure costs.

In a statement, Murray said: "The share purchase agreement imposed a number of obligations on Wavetower. These included the retention of £9.5m on behalf of the club for investment in the squad, expenditure on the infrastructure of the stadium and settlement of an agreed tax liability, together with the availability of working capital to fund the club's operations."

Whyte will not be present when Rangers host Kilmarnock on Saturday. There is a legitimate concern about whether it would be safe for him to do so. Instead, he is in London, leaving behind a swathe of fiercely negative public feeling towards him. In a statement he announced his intention to "step back from events so that I do not become a distraction to either [the administrators] or Ally McCoist and the players".

McCoist admitted "surprise" about the crucial £9m issue. "I'm the same as everyone else. I don't know where our taxes have gone. These are all questions that will have to be answered," said the manager. "I haven't spoken to Craig since Monday. We must get answers. The Rangers supporters deserve answers. My overriding feelings are of disappointment but a gritty determination to get through it."

On Friday, the statement from Whyte denied he had anything to fear. "Any fair investigation will prove that I have always acted in the best interests of Rangers and been involved in no criminal wrong-doing whatsoever," he said.

• This article was amended on 18 February 2012 to make it clear that an £18m debt was owed by Rangers to Lloyds bank.