There's no reason to believe that it would make it through three rounds of court cases within the next year, and that puts them entirely at the mercy of the justice system. It took 6 months just to get an initial decision against McGhan.
And Trump knew that Schiff and crew were more interested in getting a campaign issue than actually trying to remove him, so he knew he could easily run out the clock. Like I said, if it was really about justice, they would have gotten the courts to rule on it. They didn't.
The fact that you acknowledge this all has to be done in a year is an admission that it's all about the election.