Loss of D votes in the suburbs and Central Florida. The Democrats didn't do that bad in South Florida, racking up a ton of votes there. They performed more or less the same in South Florida, and the GOP performed the same good in North Florida. But the GOP's gains in Central Florida may have done it.
South Florida used to be a Democratic powerhouse. But those 70 year old Gore-Lieberman voters are either very, very elderly or gone. The new powerhouse seems to be white voters in the I-4 corridor and Panhandle. They love their Trump.