Can a third party intervene on the plaintiff's side in a civil suit alleging a cause of action different from the original suit's?

I want to intervene in a lawsuit currently in the US District Court for the Western District of Missouri, Kansas City. The original case (Case #: 4:18-cv-00895) is a defamation case seeking $4.755 million. The pro se plaintiff has survived the Rule 12 motion to dismiss. While I was not personally defamed, the defamation alleged did cause the collapse of an effort to stem the suicide epidemic raging in America. the plaintiff and I were working on. Unless I can become a party to this suit, I will be unable to receive compensation because I lack the resources to bring suit myself.