Has it really been that long? Apparently so. Valve originally announced their rebranding of Steam Play with Proton back on August 21st, 2018. Seems like a good time for a quick reflection being halfway to a decade old now with the tech that gave rise to the Steam Deck.
With software, it’s always the last 10% of the job that takes 90% of the work, and that’s what Valve stepped up and did.
Yes, Wine and Crossover mostly worked, if you were willing to put in a ton of effort. Valve took the time to make it damn near as easy to game on Linux as on Windows, using Windows programs.
It probably wasn’t actually 90% of the total effort, but I’m sure it took a ton of work, far more than you might otherwise think.
The 10 developers Valve hired have nearly nothing in their Github profile. Proton history is nothing but community based code and a copycat of Wine, just like everyone said in the very start of Proton.