Let's review:
1. Annoying Orange personally asked comey to stop the investigation on Flynn, who had already been fired
2. He knew at the time of Flynn's firing that he had committed multiple felony offenses
3. The definition of Obstruction of Justice includes hiding evidence of crimes from law enforcement
You have literally zero proof of that lol
Trolling, but I want to provide a serious explanation anyway. "I had to fire General Flynn because he lied to the [...] FBI." is the exact quote. If he didn't know that Flynn lied to the FBI at the time of his firing he would not have said "I had to fire him BECAUSE he lied," and would instead say something like "I'm glad I fired him, BECAUSE he lied."