A head to head comparison of the Utah 2020 Primary gives us an idea of the breakdown of voters.
Donald Trump got 58% (303k) of the vote to beat Bernie Sanders (80k votes) by 15% and Joe Biden (41k votes) by 8%.
In the Primary, Donald Trump won all 29 counties in the state of Utah, with Bernie Sanders and Joe Biden winning nothing in Utah Primary.
Bernie Sanders vs Joe Biden
Joe Biden vs Donald Trump
Donald Trump vs Joe Biden
In a head to head match up on just the total number of votes, Joe Biden (66%) beats Bernie Sanders (34%). Donald Trump (88%) beats Joe Biden (12%). Donald Trump (79%) beats Bernie Sanders (21%).
These 10 counties play an important role in these primary elections. If a candidate can get a sizable majority in the biggest county (Salt Lake), it becomes very difficult to win majorities in the smaller counties with out voter outreach and increased voter participation in them.
Donald Trump won the most votes in the state of Utah. Bernie Sanders and Joe Bernie won fewer votes. Donald Trump won all counties, hence allowing him to win the primaries in Utah.
Related References: 2016 Utah General Election Story, 2016 Utah Primary Election Story