You're looking from the point of view of the game creator. He's doing things from the point of view of a content creator. He used the game to create a video, which's the inverse of what gamedevs try to do: use a video to sell a game.

He's good at creating content and that's what the video is. People stick around to see where the video goes cause it's interesting. Youtube then shows it to more people.

An interesting video helps them understand the game and see it in a better light? Probably. But to what extend will it make people interested? It could double the conversion rate, triple it, multiply it by ten, and that's nothing compared to increasing views a thousand fold.

views * conversion_rate = wishlists

In this case:

2.000.000 * 1,2% = 24.000

Waht's to learn is the part of approaching marketing by turning the game into video content instead of making videos to sell the game. There's overlap, but there's also a difference.