I know technically they're doing it to make money, but I can't help like feel it's also something of a labor of love as well. It would have been much easier to leave people in my (our?) position behind, so I appreciate the heck out of Valve for putting in the effort. I imagine they're going to have my goodwill for a long time as a result.
When it proved hard to bootstrap that and seeing that the Steam Machine itself they started looking for options. Wine was already pretty good but DX11 support was bad. I do not know if it was serendipity that DXVK started showing promises around they same time they started looking into wine or whether it was the reason for them focusing into wine in the first place.
The rest is history, although the side effect is that it pretty much killed native ports for AAA games on Linux [2].
[1] for some values of native. Many, most, ports are based on internal close source equivalent of wine.
[2] I do not really care about native vs proton, but it would be nice if game companies did officially support proton.
It speaks more to me that they released Proton rather than shelving it after losing the original motive.
Personally I think at the very least the developers deserve equal blame for accepting the bag of money from Epic.
Money is a strong motivator but the Phoenix Point devs chose to break promises from crowdfunding to accept it. I think that reflects worse on them than it does Epic personally.
Reminder: Valve was forced to double-down on SteamOS/Linux by Microsoft's then-intention to shutdown 3rd-party storefronts on Windows. I have a complicated relationship with both Steam (as a Proton user) and Epic (for pulling Linux support on a multiplayer game I already own!), but I still appreciate more competition in the arena: GOG alone won't cut it.
Furthermore, I know some gamedevs personally who release an early access level title with exclusivity deal on epic's playform just so that they gain access to further funding to finish the game and release on Steam for the actual shot at success. They take advantage of the money to fund their work, but have said that the numbers do not compare to that of Steam.