One person notably absent from the Five Star Movement’s triumphant celebrations at a plush hotel in Rome in the early hours of Monday morning was Beppe Grillo, the comedian who less than a decade ago founded the party that seized the biggest share of the vote in Sunday’s inconclusive election.

Instead, the 69-year-old was pondering biodegradability in what appeared to be a metaphorical plea for his party to remain “unpolluted” and, if need be, return to its roots as an opposition force.

In a blogpost he congratulated the party, now led by 31-year-old Luigi Di Maio, a former waiter, but warned of the dangers of it being changed by its victory.

Grillo, who was instrumental in turning the movement built by a rabble of rebels into Italy’s strongest political force, said in January that unless it won an outright majority in the election it should remain in opposition. “It would be like saying that a panda can eat raw meat. We only eat bamboo,” he said of the prospect of sharing power.

But Di Maio, said to have been groomed by Grillo for the leadership, has other ideas. On Monday he said he was open to talks with all political parties, and he has already presented his would-be cabinet – a list of what he calls “anti-politicians”.

“Grillo remains the last major obstacle to Di Maio’s plan,” said Jacopo Iacoboni, a journalist at La Stampa and author of The Experiment, a book about the Five Star Movement. “But victory is so strong and the power of the numbers so astonishing that it will be tough even for Grillo to stop Di Maio’s plans.”

With Italy embroiled in financial crisis in 2009, it was Italians’ anger with the political establishment that helped create the Five Star Movement. The strength of feeling helped M5S win the second largest share of the vote in the 2013 elections. And now anger is again credited with driving its latest success, with Di Maio attracting support from voters who might otherwise have backed the centre-left Democratic party.

Beppe Grillo arrives at a polling station in Genoa to cast his vote in the Italian general election on Sunday. Photograph: Simone Arveda/EPA

M5S positions itself as neither left nor rightwing, and it can be difficult to understand what it stands for. In the past it has called for a referendum on the euro; now it says such a move would be a last resort.

Five Star members, especially Grillo, have long repeated discredited theories linking measles vaccines and autism. But the party recently changed its mind on that too, insisting it is not anti-vaccination, only against obliging parents to have their children injected.

Di Maio, whose father was an activist for the Italian Social Movement, a now defunct neofascist party, worked hard over the course of the election campaign to cultivate a more moderate image for M5S, including visiting London to reassure investors.

In the past, Five Star talked about pulling Italian troops out of Afghanistan and Iraq, but Di Maio now says the party is committed to Nato. He travelled to Washington last year in an effort to reconfirm the US as an ally, but he has also pledged to drop sanctions against Russia, which he describes as a historical friend of Italy.

The big question is with whom would the party ally in order to reach the 40% share of the vote required to govern Italy. Experts speculate that it could exploit the dismal performance of the Democratic party and attempt to split that party, or try to team up with the small leftwing group Free and Equal. Another scenario is a tie-up with the League, formerly known as the Northern League, a far-right party with whom it is more closely allied on issues such as immigration and Russia.

Di Maio has said he would stop sending the rescue boats that save migrants in the Mediterranean, which he has called a “sea taxi service”, while Matteo Salvini, the League’s leader, has pledged to deport thousands of illegal immigrants.

“Di Maio will try to moderate the weirdest things about the Five Star,” said Iacoboni. “But on some of the real issues I think the danger is high that we will see extreme positions.”

If the Five Star does join a coalition, it is unlikely to perturb the majority of its supporters.

“It’s a magic moment for Five Star,” said Mattia Diletti, a politics professor at Sapienza University in Rome. “They can do anything they want.”