George W. Bush was the overwhelming pick of the GOP governors and the state party functionaries. There was some resistance to him on the Hill, but he overcame that early because the party pros didn't have another horse to back. McCain was even less popular with them than with movement conservatives. He's always been a loose cannon and the professionals knew that better than anyone. Before NH Bush was widely regarded as inevitable (which he very nearly was).
There was a brief moment when a few wishful-thinking leftoids in the media thought McCain might catch him. That moment lasted from the time the polls closed in NH to the time they closed in SC. In reality, McCain never had a prayer. The establishment was with W and conservatives considered him the less imperfect of two very flawed candidates.
In 1980 it may have been Reagan's turn, but he was hardly the establishment choice. The party professionals were desperate to field anybody but Reagan. They went through a RINO Who's Who in their effort to stop him, finally settling on Bush, Sr. They didn't succeed, but it wasn't for want of trying. Reagan was so unpopular in a certain segment of the party that Congressman John Anderson mounted an independent campaign against him that netted something like 6 per cent of the vote.
The Republican apparatus is progressive and Reagan wasn't. The pros reconciled themselves to him with great reluctance, and some of them never did. Regan was the antithesis of an establishment candidate.
Maybe, but he had already fought a tooth and nail battle with Ford to prove himself a viable candidate and after his Convention speech that year, it seemed almost inevitable he was going to be the next GOP nominee.