A head to head comparison of the Nebraska 2020 Primary gives us an idea of the break down of the voters.
Donald Trump received 242,032 (62%) votes to beat Joe Biden, who received 125,335 (32%) votes and Bernie Sanders, who received 22,874 (6%) votes.
In the Primary, Trump won 92 counties in the 3-way match up. Biden trailed behind Trump winning 1 county with Sanders winning nothing in Nebraska 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, Bernie Sanders (57%) beats Hillary Clinton (43%). Donald Trump (89%) beats Hillary Clinton (11%). Donald Trump (86%) beats Bernie Sanders (14%).
These 10 counties play an important role in these primary elections. If a candidate can achieve a sizable majority in Douglas, Lancaster and Sarpy (the largest counties by voter population) they can secure the win. It becomes very difficult to win a majority of votes in the smaller counties and come out ahead.
Even though Biden achieved a 1k vote advantage over Trump in the counties of Douglas and Lancaster, Trump's steady win at most other counties (including Sarpy, the third largest) gave him the upper hand in the State of Nebraska, with Sanders getting the fewer amount of votes.
Related References: 2016 Nebraska General Election Story, 2016 Nebraska Primary Election Story