What Trump says about someone depends whether they are in the way of his objectives. Everyone is wonderful until they threaten his goals. Then they are dirt.
I don’t trust the guy one bit.
Trump’s attacks and his trustworthiness are separate issues. He does not switch from calling people “wonderful” to attacking. Most of the time he attacks the “stupid” people who he never supported. The attacks are part of his populism and appeal, but if you listen to his full speeches, they are mostly not about attacks, but about how great Trump is and how great America will be when he is president.