for some reason...not too mysterious - trump hates obama and is determined to "wipe" his Presidency away..like tearing down the statues of the old pharaohs in egypt when the successor comes to power.
   trump is a sociopath- also very insecure - no question - he can not tolerate any criticism, any disagreement or any "threat to his power".  he knows  inside himself he can not match the dignity and steady hand at the rudder that obama did. he feels compelled to not just take over from him, he want to obliterate, slur and slander the man's reputation and legacy. 
   i think he is just emphasizing his own lack of functionality,  curiosity, intelligence, education and being unable to work with someone he doesn't completely control.  i'm sure he felt he had comey and flynn under his thrumb... which he did until shooting himself in another toe and betraying and blackmailing them. flynn was his man and now he wants immunity to talk about some obviously shady dealing that came to light.