I don't have a clue what he's talking about. Another feature of conspiracy theories is that they try to bog you down in minutia.
The initial part is " It turns out that Donald Trump was conspiring with an *active* FBI informant...."
Conspiring to do what? We aren't told. Who is the *active* FBI informant? I am guessing it is this Sater person. Looked him up on Wikipedia, and it turns out that his working as an FBI informant was obviously well-known in 2015 (it was brought up in Loretta Lynch's confirmation hearing as AG that year). So I strongly doubt that Sater was an *active* FBI informant at that time, because the job requires that your connection to the feds not be known.
And typically for a conspiracy nutbar, Abramson then brings in another charge:
I see that Jason Leopold is also involved in this whole bit. Leopold doesn't have the
greatest reputation for getting the facts right.
Of course, this "scoop" turned out to be false, as Rove was not indicted at all by the prosecutor in the case, Patrick Fitzgerald. But for about a month, anti-Rove people (basically all liberals) walked around with visions of sugar plum indictments dancing in their heads. They even came up with a word for the day when Leopold's scoop would be confirmed: Fitzmas.