Nothing in extremely complex, fluid and erratic politics is a fraction as simple as this, even when the election isn't a battle between enormous powers for the future of our nation and for western civilization. It's a card, but only one we know about, and we need to respect our ignorance.
Trump-Ukraine's an example: reported to the world (us!) last spring, but unnoticed by most. Why didn't the pundits explain to us that it was huuuge and could turn into an impeachment bomb set off by Pelosi et al in the fall? They didn't know, of course. But you can bet Pelosi et al did.
Whatever. There will be a number of strategic reasons involved in not rushing the articles right over the day congress recesses for the holidays.

But one simple one is that
there's absolutely no reason not to. After all, McConnell already announced Trump innocent of all charges and promised a sham not-a-trial without witnesses.
And, gee, what might happen while they wait to get their sham show over with and behind them?
The Repubs do their best to turn time to their advantage also, but it's swarming with special dangers for them these days. McConnell has to be very afraid of the new revelations that keep happening and threatening to upset all their plans: like the new evidence the NYT presented directly to the world yesterday.
Just for more on this one type of crime among many we know he's been involved with, no one believes Trump hasn't been trying to illegally coerce
other nations to gain some personal advantage, but whatever those stories are, they haven't exploded. To date.