A head to head comparison of the 2016 Primary gives us an idea of the break down of the voters.
Hillary Clinton received 1,097,400 (27%) votes beating Donald Trump who gained 1,077,221 (26.5%) by 20,179 votes in Florida.
In the Primary, Trump won 49 counties in the 3-way match up. Clinton trailed behind Trump winning 16 counties. Sanders won 2 counties in Florida Primary.
Bernie Sanders vs Clinton
Hillary Clinton vs Donald Trump
Donald Trump vs Bernie Sanders
The total number of votes Hillary Clinton (66%) was almost double that of Bernie Sanders (34%). Hillary Clinton vs Donald Trump were both even at 50% each with over a million plus votes each, where she beating Donald by just 20K votes. (General Election too was quite a close rose among them.) Bernie Sanders lost to both Hillary Clinton & Donald Trump by over 50K votes or 32 pts.
In a head to head match up, Clinton (66%) won against Sanders (34%). Trump (66%) beat Sanders (34%). Clinton (51%) beat Trump (49%).
These 10 counties play an important role in these primary elections. If a candidate, can get a sizable majority makes it almost irrelevant from the smaller counties , you win a massive number of counties with a decent margin.
Hillary Clinton's top 10 counties of votes came from the top 10 vote size counties. She ran the board on Bernie on all of them and Donald Trump too. However, Donald Trump was able to bridge the gap to just 20K votes, because 31 more counties than she did, ending up the 50% of the votes too.
Miami-Dade and Broward, two of the larger counties voted in favor of Clinton, giving her over 159k vote advantage. Although many smaller counties voted in favor of Trump, Clinton's steady win in the more dense counties helped her gain an upper hand in the State of Florida.