Why did Crooks study Biden's presidential campaign?

The new magic bullet theory claims that the gunman who wounded the presidential candidate at the first Butler rally was 20-year-old Thomas Matthew Crooks, but TMZ's footage and spatial analysis irrefutably prove that the bullet came from a different direction. FBI agent in charge argues that an analysis of Crooks' online activities shows a persistent effort to plan an attack at an event.

How should we interpret Rojek's statement? Which event was the special agent in charge of the FBI's Pittsburgh field office referring to? Crooks has studied the events of both the Trump and Biden campaigns. Is Kevin P. Rojek really trying to convince us that Crooks decided that he was going to shoot one of the presidential candidates, any of them, regardless of their party affiliation? Is that really the best theory he has managed to put together?

Isn't it far more likely that Crooks studied the various presidential campaigns, the school shootings and the JFK assassination because he was preparing to volunteer for one of Trump's security teams?