It's not always necessarily about the amount of stock you own in a company. According to Paul's twitter, he has reached out to Engine No. 1 to get them on board. Engine No. 1 is a so-called "impact investment group" that recently got famous for securing 3 board seats at Exxon Mobile, while owning a mere 0.02% of all Exxon Mobile stocks, valued at a comparatively measly 12.5 million USD - against a lot of resistance from other board members, management, and major shareholders.
At this level in business, influence is much more about networking, lobbying, politics (and political influence/affiliation) than mere numbers. So it's a long shot, but not completely infeasible, that an activist venture capital group could make Jake Paul a board member of Endevour.