Democrats know they stole the election and Trump is still the legitimate President.
That's why they must do everything possible -- impeach, convict, prosecute, insult, jail, whatever they can -- to nail down the coffin lid on his presidency and prevent him from ever rising again politically.
Couldn’t agree with you more that their core motive is as you outlined. Fear. Of Trump’s return. Heck, the people miss him already. The buyers’ remorse will only deepen with time.