As another reply said, Florida is the third largest state, with the third largest number of electoral votes. Since electoral votes are winner-take-all (with a couple of exceptions), all you need is a tiny minority to make a huge impact on who wins the Presidency.

The two largest states reliably vote the same way in each election, but Florida is at least somewhat up for grabs. So Florida is one of the most important opportunities to make a big impact with a small advantage.

If this seems like an incredibly stupid way to run things... yes, we know.