People are competing for control of the Democratic party and they're doing a lot more than shitposting on the internet or sending $15 to their favorite candidate. They're spending lots and lots and lots of money and other resources even as elites bemoan "purity tests" and similar from the great unwashed. Every rich guy who maxes out to a candidate in the primary has a much more rigid purity test, backed up by money and power, than jerks on the internet do.