I didn't have Subnautica either, a nice game to have as the first game of my Epic Games library (not taking Fortnite into account).

Steam's new revenue share was actually announced a few days prior to Epic Games announcing their store. I doubt it was a coincidence, Valve must have known what was going to happen, they just didn't know how low Epic Games' commission would be. Epic Games still isn't the best one in terms of commission though, itch.io has for a long time allowed developers to set itch.io's commission percentage and Discord just released a statement about lowering their commission to 10%.

I believe too that most developers using Unreal Engine will migrate to the Epic Games Store. They are the ones that get the most advantages from this. I also believe that a big part of AAA games that don't already have their own platform will switch to Epic Games. It's all about money for publishers of those games after all. This proved to work in the past with platforms like Origin, Uplay and Battle.net, I have no doubt it will work again with the Epic Games Store.