You have it wrong. They failed to signal to the establishment that Romney was unacceptable. And then when Romney was anointed, they failed to walk out of the room.
The Tea Party that I have seen so far is a toothless pussycat and the establishment/RINO party knows it.
It wasn’t their job to signal those people. It was to vote for someone else. They instead kicked one candidate after the other overboard because of BS.
And in the end they did walk. That is why Romney got fewer votes than McCain did.