I'll give ya that one - Trump did do that. But after Trump received the nomination, he was as cordial as could be towards all the beaten Republican candidates. Sadly, Trump did not get a friendly congrats from some of them, and so Trump responded in kind.
You repeatedly call a man a liar, mock a man's wife and accuse his father of having something to do with the Kennedy assassination, and you expect cordial relations afterward?
In times past, there would be bloodshed over what was said.
You must admit...Ted Cruz was a bit out of line with his speech at the convention, and he got roundly booed for it. What was Trump supposed to do, hug him right after that?
Ted Cruz was not out of line. The people who were out of line were the ones expecting Cruz to do anything more than support the party that had treated him so shabbily.
Trump refrained from using the nasty tactics on Cruz until it was clear that he wasn't going to beat Cruz unless he did. For the longest time Trump and Cruz were very cordial to each other, but that all changed when Trump launched the "Lying Ted" meme, which his followers immediately repeated ad nauseum like trained clapping seals.
I actually expected Trump to do this, but I was still disappointed when he did. I had hoped that the two candidates could carry on their campaigns without having to get nasty at each other, but that was a forlorn hope.
To Cruz's credit, he has put the interests of the country ahead of his all too understandable grudge against Trump.