They're not doing more though, so I can only conclude that they're not at all convinced that they're unconstitutional.
To be fair though I have no idea what Trump is thinking, I don't think anybody really does. He might actually believe what he's saying in this instance.
They don't want to be to aggressive so that when their team is in control they can utilize that power.
This is an affliction of both parties and to take a more philosophical view, "power corrupts".
One of the meta-arguments for smaller, less powerful government, is to minimize abuse of power or shift it more locally (state, muni) where the abuse can be more visible if not contained.
Good rule of thumb: Don't advocate for a power or control that you wouldn't be comfortable with in the hands of your political opponent. Unfortunately I think that the Democrats and the Republicans are more comfortable with passing many powers back and forth between them rather then eliminating them.