Are successful people likely to be success stans?

From personal experience, no. When you are successful, by habit for protection, you realize it's better to not bring attention to your successes because there's a lot of jealous and covetous people, and they could try to destroy your success or hurt you in some way. And this precaution extends to others you care about. Hence I feel like successful people are much less likely to be success stans. So while they could still be fans of top groups, bragging about their successes (charts, ranks, sales) isn't something they do.