that link is pretty vague on specifics. It lists unreal first at the top but it's not clear that it's sorted by usage or just by their recommendation on what to use. To be frank, I don't like unity and I'd personally use unreal over it, but I'm just pointing out that unity makes up a lot of games.

If you scroll down it even says

The most used game engines in the industry are Unreal Engine and Unity. These engines have a large user base and are widely adopted by game developers.

Again, without measuring or indicating which is more. This article has some some statistics from steam and itch and admits it's difficult to count. The results from itch are more trustworthy because of how the data is gathered but you start getting into "what counts as a game"? There's more information here on usage including that it makes up 90% of games on VR platforms.

It's difficult to measure because games aren't required to publish this information, but depending on what counts as a game (do hobby games released on itch count?) it can be a significant amount.

It definitely isn't the most used how on earth did you come to that conclusion? It's increasingly popular definitely and it is a good engine but it's not the most used.

Unreal Engine 5 is a relatively new product and Unreal Engine 4 was basically on par with the Unity, so there wasn't a great reason to use it over unity especially considering the Unity had the developer community behind it. Even now Unity still has more community drop-ins than Unreal.