David P. Goldman (also known as Spengler), writing in Asia Times , writes of the suspicions that trouble me as well:

The stock market plunged Tuesday, and with futures trading down heavily before the market opens shortly, it looks as though the market will have erased all of the gains in 2018 when trading resumes. The development that seems to have triggered this rebuke to President Trump's boasts about the stock market was an unprecedented event: the arrest in Canada of the chief financial officer (and daughter of the founder ) of Chinese electronics giant Huawei, on a warrant from the U.S. over alleged violations of the Iran embargo.

[N]ever before has the United States attempted the extraterritorial rendition of a foreign citizen – Meng [Wangzhou] is a Chinese national – in connection with sanctions violations. It has imposed travel and banking restrictions, but seeking an arrest warrant for this is entirely without precedent.

The timing was precise:

Meng was arrested on December 1, the day that President Trump and his economic team dined with President Xi Jinping and his advisers at the Group of 20 Summit in Buenos Aires. Trump has every interest in striking a deal with China that would enable him to declare some measure of victory in a trade war, and China has shown every indication that it is willing to make concessions to the United States on intellectual property protection, financial market opening and, at least in rhetoric, on industrial policy, while increasing its imports from the United States. The question is: Who ordered the arrest, and why?

Goldman sees two general possibilities: that Trump knew about and approved the arrest (despite the probably negative effects on the trade deal he seeks) or that he was not witting. If the latter is the case, it is possible that the intent was to go hard-line on China, weakened by Trump's tariffs, before it becomes too powerful to resist. But the other, much more troubling alternative is that entrenched anti-Trump forces carried out the arrest in order to sabotage the trade deal, and with it the stock market and economy.

If Trump's economic miracle reviving the economy from its Obama-induced doldrums turns to ashes with a recession, there likely will be a Democrat inaugurated as the 46th president in 2021. Roger L. Simon at PJ Media sums it up:

If Xi doesn't make a deal with Trump on trade, we are almost certainly headed for a recession (or worse) and Donald will be out the door.

Goldman analyzes who might have ordered the arrest without Trump's assent (emphasis added):

The sanctions regime against Iran is the responsibility of the Treasury's Office of Terrorism and Financial Intelligence, now directed by Undersecretary of Treasury Sigal Mandelker, a law enforcement veteran who served in the Bush Administration after the 9/11 attacks and advised Homeland Security Secretary Michael Chertoff during the George W. Bush Administration. The Office of Terrorism and Financial Intelligence is a joint project with the Central Intelligence Agency. Undersecretary Mandelker's predecessor in the position, attorney David Cohen, subsequently became a deputy director of the CIA.

There is no way to know if a conspiracy of Trump's enemies is underway to hand the presidency to the Democrats by undoing the economic and stock market gains of the last two years. The 2008 financial crisis worked like a charm.

I wish I could rule out an effort to harm the trade deal for political purposes, but I can't.