They paid out those who bet on a Hillary win. If trump wins, those who bet on a Trump win would also be paid out, the contract is not cancelled.
Read Paddy Power’s article on their website, it’s actually fairly balanced. Says they’ve gotten decisions wrong before and if Trump wins it will trigger the biggest payout in political betting history and leave very expensive pie on their faces.
This is a free publicity move to attract more gamblers for their much more lucrative sports book. Paddy could have also insured themselves against a Trump win as well given the low odds.
That’s just too odd, and another reason I don’t gamble.
One assumes that like any bookie they pay the actual winners and the loser gets zilch.