Based on what? He was certainly not leading in any of the polls. He was completely clobbered in the campaign air war then as well. Biden was everywhere - Trump was nowhere...not a winning formula. Trump was having to pull ads from some places and put them others due to not having enough resources to stay up on the air in all battlegrounds. Biden also advertised heavily nationally on many networks where Trump had zero presence - targeting older demographics...and it worked as he made gains with those voters, enough to affect the outcome of multiple states he very narrowly won. Granted, the media covering up the laptop story and the like *also* was enough to have affected the results of multiple states with razor thin margins, as well as ballot harvesting and shenanigans with the ballots.
We remember differently is all, sorry