I’m pretty sure stars are based more on replies to your posts than just upvotes. I think a user got to 4 in like 120 posts without a huge number of upvotes but by mainly rage baiting. My first two posts had only ~60 upvotes but I got 1.5 stars basically immediately from a fair number of replies.
Stars are based on your activity, not upvotes. The more you post/reply, the more stars you get. I remember this was somewhere in the settings explaining this before but I can't find it now.