They believe it because in the past he was clearly shown to have been funding some movements through the Open Society Foundation which he created. Organization for Black Struggle and Missourians Organizing for Reform and Empowerment are two the he has funded with his Open Societies Foundation and both of them which were supposedly headquartered in Missouri ended up stirring up trouble in Florida when Trayvon Martin was shot. Then you add in that some government around the world have banned Open Society Foundation because of what it tried to do. The problem is that no one know exactly where he tries to do things because he uses a foundation that then uses other groups and so on to make it very difficult to know exactly what he is doing or who he is trying to help... worse still is that instead of trying to help a particular group or achieve a particular goal he tends to help organizations that have goals related to changing governments policies like trying to get illegal citizens and turning them into American citizen. So he pushes alot of buttons which leads to him being turned into the boogie man. Frankly he probably does do some shit that isn't good and other things that are helpful. But because he tries to be so secretive he ends up looking guilty.
Oh, aren't we showing your complete lack of intelligence. You've just managed to get lumped into the illustrious group of liberal half wits that run around squawking "homophobe" and "Racist" simply because you were trained to say it whenever someone dares to bring up the truth you don't want to accept. You should realize that when you just go squawking antisemite that normal people just write off everything else you say because they know it came from a liberal parrot.
I'd suggest that you do a little more research before you start calling people 'nut jobs'. It's all too fashionable these days, (particularly after all that has gone on in the last three months with the virus and this latest distraction) to call people 'nut jobs' when there are just too many 'coincidences' cropping up that are causing chaos and destruction. Research the man's history and what he has been involved in.
I like how his detractors call him a Marxist yet he's a hedge fund/Wall Street shark who probably knows more about and practices cutthroat capitalism than all of these low-income GOP suck ups who scream about Socialism because Sean Hannity and Laura Ingrateham told them to.