22,000 Floridians were purged from the voting roles illegally, almost all of them were Democratic and over 50% of them were African American. Florida state law later found that 95% of these voters were innocent of any crime and since the Floridian official tallies gave Bush a 537 vote lead these 22,000 votes would give Al Gore the advantage and flip over the 25 electoral votes for Gore!
Al Gore's personality is what lost him the election, not the felon disenfranchisement law. If Al Gore were able to relate to ordinary people more strongly, he would have had a better chance to win the election, and the political theater that played out in Florida would not have been relevant.
If Gore depended on the rights of felons to vote, he didn't deserve to win the election. He needed a significant margin of electoral votes to beat Bush in the 2000 presidential election, and he just didn't get the votes he needed. It didn't depend on a single factor but on the fact that he simply wasn't electable.