My take is that none of the candidates get to 1,237 so there is no consensus candidate on the first ballot. The establishment takes the position that the candidates have all been rejected by the people because they didn't get to 1,237 after all the primaries/caucuses. The establishment then nominates Paul Ryan - who, much like the Speaker position, says he doesn't want to be the nominee but ends up accepting out of "duty" to the party. The Trump and Cruz people freak out and don't vote for Ryan. GOP loses.
Establishment won't care because they were going to lose with Trump or Cruz anyway. They can then spend the next four years criticizing Hillary, the Dems and take their shot in four more years with someone else. The point is they stay relevant during the four years Hillary is in office and remain in positions of power. If Trump got elected he wouldn't be listening to the establishment strategists, lobbyists, pollsters, donors, etc. So they would lose relevance/power over the next 4-8 years without control over the President. Cruz would do things "his way" as well although not to the extent Trump would. That is why the establishment has never liked Cruz - he doesn't play by their rules. They only back him now because he is a way to block Trump from getting to 1,237 so they can handpick another nominee at the convention.
Problem is if the establishment goes the contested convention route and handpicks someone like Ryan then Cruz likely resurfaces in 2020 and runs for President again. He can argue the nomination was stolen from him and he would have beaten Hillary. Voters who don't want the establishment will likely vote for him again. (Trump likely be out in 2020). So the frustrated GOP base will still have Cruz as an option in 2020 to push back at the establishment. If the establishment wanted to clear the decks for 2020 they should nominate Cruz at the convention. Trump can bolt and go third party, and the GOP with Cruz as its candidate loses. That sets up the table so that in 2020 the establishment can say to the people we tried your option with Cruz and he lost so he is now a tainted candidate we can't support in 2020. Trump bolted the party so we need to get back to a true conservative option for the GOP to support in 2020 - then they pull out someone like Ryan, or whoever they want at that point and support him. They get "their" party back that way rather than steamrolling Cruz and Trump at a convention and handpicking someone (who will lose anyway so why not have Cruz be the sacrificial lamb).