I'd be interested to see a study that explores the behaviour behind wishlist conversions, but I can speculate based on my own behaviour.

It's an open secret that wishlisting helps indie games. These studios can't compete with the marketing budget of larger studios, so discovery might be limited to whether or not the algorithm picks up the game. Successful games will typically have a store page appear shortly before release encouraging you to wishlist the title. If it gets a lot of wishlists, it might appear in "Popular Upcoming" lists which helps it grow even further, and then is more likely to appear on Steam's front page when the game releases.

Wishlisting costs me nothing to show support for a game. However as much as I would like to, I can't financially support all the games that I think are neat - there's just too many of them. So when I see an indie game that has appeal, I'm primed to wishlist it, but I can't purchase all of them. Therefore, lower conversions for indie games.

Now on the flip side, there's high budget games for major studios. I can't afford to spend $100 for a new game, so if there's a game that looks appealing, it's going on the wishlist because I'll get a notification when it goes on sale. In this sense, I'm motivated to only wishlist those games that I actually wish to purchase, and do intend to purchase them when the price reaches an acceptable level. Therefore, higher conversion rates for larger studios.

Although the data from the linked article comes from this article, and they're primarily concerned with Week One conversions. So my shopping behaviour for games from large studios doesn't really factor in because those games won't go on sale until several months after release. I suppose what's more likely is that people are shying away from pre-orders, and are using the wishlist to be notified when the game releases. Then depending on how launch weekend goes, they might buy the game.

Large studios with big games tend to open up their store pages long before smaller indie titles do. That's part of their hype and marketing strategy, but it's also to help them fish for pre-orders. In today's landscape, you'd be a sucker to pre-order a game. However, if I know I'm likely to purchase the game after release and want to know when it's released, a wishlist can be a helpful notifier. And now we're back up to higher conversion rates for large studios.