As far as I know jersey sales are dependent on stats, NT, and Allstar game selection (earns you an extra 3k apparently, but I'm not sure if it's division dependent).
You're a supporter - so it easy to see his stat rankings. He's ranked top 5 in your league in several stats. That is why he is earning quite a bit of jersey sales. Jersey sales are calculated by percentage - 5k out of 50k+ salary means he's just brining in 10% of jersey sales. I assume one of those steadily earning 1k jersey sales a week is Ernie Papi Tiu. If he earned 50k per week he'd probably have a similar amount of merch.
So nope, it doesn't matter how many championships he won. All that matters is how many games he played this season and how much numbers he puts up.