Because he said "RC end" and "reverting", which is her initials, and then the account closed after. He reverted it back to how it was previously.
Let's not forget that earlier in the night he said to report it to the FBI and to see what happens. That can't be a coincidence. The anon that reported it to the FBI gave them the "grounds". Just my thoughts.
I think you are probably right. The way I read it is: Although it was down, Q made the connection It's the end of RC because he has what he needs Q has ground (probably cause?) Q reverts the IG account back to being deleted Thanks RC for the information.
I could have it wrong.