Bleeding Heartland has this very comprehensive article about Iowa ballot access laws. In 2019 and again in 2021, the legislature changed the laws to make them more severe. As a result, the number of candidates running this year, who are not Democrats or Republicans, is much smaller. The article correctly points out that the 2019 lawsuit has been in front of a federal judge for an entire year (since the briefs were filed), and the judge still has not ruled.