So Trump, who has bent the rules for years, is complaining about someone who played honestly by the rules?
It goes with his whole Big Man shtick where he's going to use the strength of his personality and negotiating skills to get results for America regardless of common sense, controlling legislation, treaties or other jurisdictional issues.
It appeals to his base because there is an animus towards "rules lawyers" (many of whom are actual lawyers) who know the rulebook or bylaws inside and out and use that to their advantage in a way that seems unfair.
I feel it is well. If you /playplayed tabletop RPGs or tactical/strategic board or miniature games you've encountered these people. Also, if you were ever a reporter who had to cover the politics beat you've encountered these people. And some of them are absolutely horrid individuals. Members of HOAs know at least one of these sorts.
Full disclosure: In RPG terms I may have min/maxed a character or two in my day and got the evil looks from the others so I'm no angel in this regard.
So I understand the anger, however this is a high stakes game Trump is involved in and insisting that an opponent refrain from using every available rule to gain an advantage is just juvenile.
It's literally complaining about someone being more skilled than you and demanding they play down to your level.
If Trump was running against an opponent that had less money would he give him enough money to bring them equal? No, I don't think so.
How about helping opponents get on ballots that they otherwise could not for some reason? No?
Or if his ground game was better than Cruz's and he beat Ted in the Colorado delegate race would we have heard about this at all? No?
Trump is a big crybully with feet of clay who's ego is way bigger than his skillset but his supporters see a BMOC who will teach them nerds, pencil-necks, and dirty foreigners a lesson.
