In hindsight, Trump winning Florida (by a lot, even) was practically written in the stars. Aside from terrible polls, all the evidence on the ground indicated that Republicans had an advantage. They were making big gains in voter registration, were over-performing in the early vote, seemed to be making big gains with Cubans, and had the advantage of a good ground game as opposed to none at all. I was surprised by the disaster in Florida, but I really shouldn't have been.
The warning signs were there in 2018. A shockingly large amount of Clinton voters in Miami-Dade flipped to Ron DeSantis and Rick Scott. Were it not for them, they both would have lost.