Cruz is a first term senator that ran on a Tea Party platform. The "GOP establishment elite guys" drew a target on his back the first day he was there.
I think the Tea Party thing was pretty much an act much like Rubio pulled. The Senators all knew who Cruz was from his association with Boehner and Bush. I think the reason they dislike him as they do is that he committed the grave sin of jumping the line. As the GOP insider said in the restaurant scene on “The Circus” “Republicans are respectful and wait their turn”.