During Watergate the simple question was : What did the President know?
In this case the equivalent question is : what did Candidate Trump know?
If he "weighed in" on the original sketchy response when news of the Fredo meeting broke then he must have known all about it by then at least. Unless he was still being deceived, which is surely not a claim Trump would ever make. He might allow his lawyers to make it, but he'd tweet a denial right after and then bring it up at his next rally. "I so knew who was at that meeting, there were some great people at that meeting, on many sides, many sides".
They've already admitted this. With this, he's confessed at least twice to committing obstruction of justice (the Comey firing interview with Lester Holt being the other occasion).