This makes perfect sense if you understand the fact that Drumpf is a fiercely distorted arrested-development case. His emotional age is frozen at about 9. An ill-mannered spoiled-brat 9. Of course he brags to his mentors because they are representative of the man he thinks of as his spiritual big brother - Putin - and Drumpf desperately wants approval from him. This is a classic example of a childish ego seeking validation that he never got from his own parents.
This is also a classic example of the incredible stupidity that Drumpf has displayed since day one of his campaign, and which his sycophants still refuse to admit, God damn them to the hell they so richly deserve. He actually believes that all he had to do to stop the investigation was to fire someone. He is such a brainless clod that even if he didn't have the the raging egomania that makes him believe he can sway anyone with his trademark creepy handshake and a few words, he is utterly incapable of understanding how he has convinced everyone in Washington, even about half his own party, that he is so incompetent he is a danger to this country and should be removed from office.
GOD DAMN THE LEADERSHIP OF THE REPUBLICAN PARTY. With their eyes wide open and with full knowledge of what they were doing, they cursed this country with a "President" who has the IQ of a pig, the sense of responsibility of a pig, the manners and morals of a pig, the humanity of a pig, and the social grace of a constipated pig.