The whole story is that this is Hunter Biden's laptop, but in reality some random dude dropped it off and the owner said that "he had a medical condition that prevented him from actually seeing who dropped off the laptop but that he believed it to be Hunter Biden’s because of a sticker related to the Beau Biden Foundation that was on it." [1].
Then, it gets passed off to Trump's personal lawyer Rudy Giuliani back at the start of the year when Guiliani is already trying to get Ukraine to stir up a story on Hunter Biden. They then sit on it for most of the year and release it 20 days before the election.
Something like this, even as absurd as it is, will take weeks to thoroughly debunk. Meanwhile, people are literally in lines voting and stuff like this has an effect. That's probably why it was released right now, because even though it's most likely false, by the time it has flown around the internet unimpeded the damage will have already been done.
[1] https://www.thedailybeast.com/man-who-reportedly-gave-hunter...