Since Jan 6, he's acted strange, has not said anything. However just before leaving he's said "the best is yet to come" and gave list of accomplishments. He hasn't been dooming over the "new administration" either.
For the record this is not a thread about "the plan", but I definitely think something fishy is going on from Trump & allies' side that would be nice if we knew the answer to, even if this isn't "the plan".
They are holding him hostage with the threat of impeachment. They don't want him criticizing every move the Biden puppeteers make.