Jeb and Crist (when he was a Republican) were both personally popular and well-connected. Rick Scott never enjoyed personal popularity, and defeated Nelson only because Nelson was old, tired, ran a poor campaign, and whose personal popularity died with those folks who crossed party lines to vote for him in Brevard and Indian River Counties back in the day.
DeSantis is making all the right moves, and is proving to be exceptionally popular. I believe he may well win re-election with over 55% of the vote, and I believe he will cause serious challengers to opt out of the 2022 FL Governor's race. (Such a result would not be a reflection of where FL is at as much as personal approval of the candidates.
Concerning the 2018 senatorial race, Scott saw a surge in term of popularity after 2016 and it was clearly a major factor in the loss of Nelson