Trump cost me my Senate seat so I’m going to stab him in the back. Occam’s razor.
That and the cowardice he showed, giving into the screaming.
Actually, it was Dr. Kelli Ward who scared him out of the Senate and as thanks the electorate nominated Flake light and not Ward.
Occams razoryes! Flake (as well as dead man McCain) HATE/HATED Trump. Their bitter jealousy of Trump as a successful and popular POTUS drove/drive everything.
Judas Flake was disrespectful and nasty to Trump every day, and his pettiness drove his approval numbers to below 18%. Now he is a failed first term senator and is going scorched earth.