Instead of getting all the delegates from these wins, he has to share 311 of them with a bunch of losers under the "rules", people who would otherwise be forgotten by now but for Republican elites' failure to tell them to go away as they would have in the past.
This is why voters hate the Republicans. They don't want to win, and they don't want anybody else to win, either, and have designed their system accordingly.
Republicans govern the same way. It's more important to them to follow a bunch of self-imposed rules (read "principles") than to do what the American people need. Free-trade and open borders uber alles, no matter how many people are hurt.
Trump has already surpassed the total vote received by both McCain in 2008 (9.9 million) and Romney in 2012 (9.8 million), but we'll still hear the Mark Levins and Rush Limbaughs of the world today failing to get behind the obvious new leader of the Republican Party while the remaining contenders for the nomination seal their ignominious reputations by refusing to concede.