Could this see the collapse of the party if they don't succeed?
Well, hypothetically anything could, but frankly I don't think it particularly likely, at least for the commonly understood idea of "collapse."
For one thing, it's critical to keep in mind that Congress acts nationally but its members are elected at the state level, and plenty of states are so deep red that the RNC is essentially superfluous. Alabama, for example, will keep on electing conservative candidates to its state offices no matter what happens; they could be Republicans or The $$ U.S.A. Flag Eagle $$ Conservatives or lizard people from Mars and they'd still get elected in a landslide so long as they promised not to be a damn dirty godless liberal commie. No matter what happens to McConnell and Ryan and Meadows and Cruz, there will still be a roster of state-level politicians with which to populate a conservative primary -- so in that sense, the Republicans will live on even if the Republican party does not, and whatever successor they have will probably keep much of the same platform. There will also be enough ultra-capitalists disaffected with their treatment at the hands of the Democrats to fund them.
In that sense, then, all the elements of a short-to-mid-term successful Republican-like party are in place: people, votes, and money. More likely than an outright collapse is a very public and bloody changing of the guard, with various high-profile Republicans stripped of things like speakerships and majority leaderships and leadership of the RNC and held up as "the Republicans behind Trump". The Meadows/Cruz wing of the party may veer hard right to pick up legitimately crazy donors like the Mercers and force the rank-and-file to reform under their banner; it's a dead end strategy, but one they can milk for years. Impeachment would almost certainly be part of that process, particularly since Pence's evangelical appeal can help direct most of the fallout from that process at the moderates in the party.
They are, in that case, doomed: their most natural inclination is to swing older, whiter, and grumpier, which only works so long as those people stay alive, since demographics suggest they will be impossible to replace. However, the gigantic, collapse-looking paradigm shift leftward won't happen in that event until the Boomers die out.