Overall you're right - RCV will exert huge pressure on candidates to move to the middle. But it's not 100%, and I think Trump is a specific example of how it's not a 100% effect. Trump got the nomination precisely because he was hugely popular, the #1 Choice, in half of American society. In RCV, he would top the rankings of those people and continue to the final round, which, well we all know how that turned out. Trump won.