There was a huge amount of work by WINE (and others), but it really was a huge leap in how accessible Linux gaming was to people.
Going back a few years, my experience was that you had to do some research to see if a game was likely to work, install it through wine, and then usually faff around with a load of winetricks/configurations/packages/etc to get a game that mostly worked (often with some weird bugs, performance issues, etc).
Now there's a whole library of games that you can just right click -> install and they work perfectly well on Linux. And of course that wouldn't have been possible without the years of work building up to it - but it was a massive improvement when Valve threw their weight behind it and built it directly into the Steam client.
Going back a few years, my experience was that you had to do some research to see if a game was likely to work, install it through wine, and then usually faff around with a load of winetricks/configurations/packages/etc to get a game that mostly worked (often with some weird bugs, performance issues, etc).
Now there's a whole library of games that you can just right click -> install and they work perfectly well on Linux. And of course that wouldn't have been possible without the years of work building up to it - but it was a massive improvement when Valve threw their weight behind it and built it directly into the Steam client.