16 V 2020: Why did Trump fire the Inspector General of the State Dept?

Trump announced his dismissal of the Inspector General of the State Dept., Mr. Steve Linick, who has served in that capacity since 2013, and replace him with Stephen Allard, an Indiana crony of V-P Pence. Trump says he has lost confidence in Linick. That means “He might be a whistle blower.” Why did he lose confidence in Linick? Linick has initiated an investigation of Secy. Pompeo’s improper use of a political appointee as a houseboy. 

Commentators say this replacement of someone who can be trusted to do his job with a crony who can be trusted not to do his job is the latest manifestation of Trump’s paranoia about anyone who has not sworn the oath of unconditional obedience and loyalty to him. I agree with this conclusion, but I feel there is an additional inference to be made: Trump fired Linick because Pompeo is guilty and Linick knows it