Cart before horse, confusing cause with effect, etc.
Oh, sure, they'll try to destroy him. They've been trying to destroy him. But they kept talking Trump all these months because that is what has gotten them ratings.
Part of the reason Trump is so teflon to scandal, or even the consistency in what he says/promises on the campaign trail, is that most of his supporters despise the mainstream media. They know, either directly, or instinctively/subconsciously that the media is "part of the problem" that they're railing against with their Trump support.
So a big part of Trump's success is a lesson the rest of the GOP learned far, far, too late, and probably still hasn't learned. The more the MSM is gunning for you, the better the job you are doing.
For everything else wrong with him, Trump's view is that the MSM "works for him", he's not their trained monkey. That he should ever try to appease the media is insanity to him. The media is the maids, the help.... And whenever they try to use him as their trained monkey, or a foil, it just backfires. At a minimum, whatever hits to his reputation negative coverage causes, at worst, it's a wash, because he gets it right back in his voting base's respect for the honeybadger attitude.
The conventional wisdom that "T
hey haven't even started to bash Trump, wait until he's the nominee..." will most likely backfire spectacularly.
And as pundits and protesters, SJW's, lefties, Illegals etc. all protest harder and harder, Trump is going to look more and more appealing to even those who currently have #neverTrump sympathies. (That and my own MSM disdain... It's certainly the only thing I like about him) Even knowing there's about a 99.5% chance he'll be a Pyrrhic victory.