A head to head comparison of the Iowa 2020 Primary gives us an idea of the break down of the voters.
Donald Trump got 92% (31k) of the vote to beat Joe Bider (340 votes) by 1% and Bernie Sanders (562 votes) by 2%.
In the Primary, Donald Trump wins 99 out of the 104 counties in the state of Iowa. Bernie Sanders trailed behind Trump winning 4 counties. Amy Klobuchar wins 1 counties but Joe Biden winning nothing in Iowa Primary.
Bernie Sanders vs Joe Biden
Joe Biden vs Donald Trump
Donald Trump vs Bernie Sanders
In a head to head match up on just the total number of votes, Bernie Sanders (62%) beats Joe Biden (38%). Donald Trump (99%) beats Joe Biden (1%). Donald Trump (98%) beats Bernie Sanders (2%).
These 10 counties play an important role in these Primary Elections. If a candidate can get a sizable majority in the larger counties (Polkn Linn, Scott), it becomes very difficult to win majorities in the smaller counties without voter outreach and increased voter participation in them.
Donald Trump won 99 counties, securing him the victory in the state of Iowa in the 2020 Primary elections. Donald Trump won because he won so many counties. Bernie Sanders only won 4 counties and Joe Biden did not win any counties in the state of Iowa. Winning at many other counties helped Donald Trump gain an upper hand in the state of Iowa.