If Corbyn had claimed seven more seats, the total seats won by Labour, the Lib Dems, the SNP, Plaid Cymru, the Green Party and one independent MP would have come to 322 - enough to dethrone the Conservatives of their power.
May's miscalculation in calling this election harks back to an earlier blunder by her immediate predecessor: former Prime Minister David Cameron and his decision to hold a referendum on "Brexit" in the first place. "Over the next five years build a country in which no one and no community is left behind, a country in which prosperity and opportunity are shared across this United Kingdom".
Theresa May was fighting for survival on Saturday after a failed election gamble undermined her authority and plunged the country into a major political crisis days before talks to leave the European Union start.
Given May's diminished state, many in the European Union are wondering how long she will be leading the country and - by extension - the Brexit negotiations.
Agreeing a position with the DUP is going to be "very hard for May", argues Bronwen Maddox, the director of the Institute for Government, a think tank.
A deal between the government and the DUP could also unsettle the precarious balance between Northern Ireland's British loyalist and Irish nationalist parties. Corbyn pointed out that the police force was cut by nearly 20,000 during May's tenure - which was not a message to make the general public feel more secure in the aftermath of terrorist incidents. She has brought weakness and uncertainty.
The DUP, whose 10 seats would allow the government to get measures through Parliament, is a socially conservative pro-British Protestant group that opposes abortion and same-sex marriage and includes both environmentalists and climate-change deniers among its senior ranks. "What tonight is about is the rejection of Theresa May's version of extreme Brexit", said Keir Starmer, Labour's policy chief on Brexit, saying his party wanted to retain the benefits of the European single market and customs union.
Surprisingly, Nigel Farage of the United Kingdom Independence Party, which had stridently campaigned for Brexit, on Friday called for a fresh vote on leaving Europe in light of the election result.
In contrast, Conservative voters were more likely to know from the outset which way they were voting, Lord Ashcroft said. Having announced a so-called "dementia tax" which would use the value of people's homes to fund their care in their old age, she backtracked in the face of popular opposition.
He said May was chosen by the Conservative Party last autumn to be the safe pair of hands that would navigate Britain through the hard waters of Brexit.