It wasn't clean. Trump won by that much.
One theory is the DDOS attack on the east coast a month or two before the election was the white hats unrigging a number of machines.
Trump knew this election would be riddled with fuggery, he even tweeted about Broward County trying to cheat him in 2016. Now he has proof, and reason to demand voter IDs for 2020. Voter ID will be the death of the DNC.