I find it fascinating how many of Trump's supporters are shocked and horrified when he inevitably turns on them. There is an Aesop fable about a farmer finding a near frozen viper, feels sorry for it, takes it into his coat to warm it, only to be lethally bitten as the snake revives. When the farmer berates the snake with his dying breath, the snake says, "But you knew I was a viper when you brought me into your bosom. What did you expect?"
I've seen this over and over again with Trump in many contexts. And now it's the Republican Senators who are shocked that this mean, nasty, vengeful, petty little man with a lifelong history of scapegoating, humiliating and deep-siding his aides, staff, and supporters has actually turned on one of them! How unexpected! Presumably they thought that Trump was only a cruel, evil monster toward little, powerless people. Not important people such as ex-Senators like Sessions. Apparently the former was just fine, but the latter is crossing an ethical line.