I'm curious, what exactly makes Bazzite a gaming-focused distribution? Like, it comes with Steam preloaded, I'm guessing, are there other aspects to it?

As you correctly guessed already, indeed, Steam is included by default. Beyond that, we got some of the usual suspects:

• A lot of other OOTB enabling (like e.g. OOTB Nvidia driver support, controller support etc) that one might like on a system used for gaming
• The use of another kernel + scheduler (and probs more) for improved gaming performance
• Depending on the image you install, you get Steam Gaming Mode OOTB; i.e. the UI found on the Steam Deck
• It's perfectly suited for the console experience, because of how seamless everything works by virtue of the automatic updates in the background + updates being atomic + built-in rollback functionality + the amount of control the bootc model gives for image management to the image maintainers

It does a whole lot more than that, but the above should probs suffice.

I used to distro-hop a bit back in the late 00s, and while it was fun to see what the different distributions bundled and whatnot, it never felt like something was particularly suited for one thing or another.

Hmm..., FWIW, Ubuntu Studio has been around since 2007. I suppose it's basically the same idea, but directed towards creative use rather than gaming.

I'm now on OpenSuSE Tumbleweed, and it's just... Linux, I guess? I play games on it, VR, what have you, and it does what I want it to.

To be clear, Bazzite can perfectly work as a general use computer; especially for those that appreciate the bootc model but would like to consume it through a popular 'image'.

If you're running Nvidia, it includes the official drivers OOTB and keeps them updated. There's also stuff like WINE and Lutris already included, udev rules to make sure all controllers just work. For handhelds or home theatre PCs it includes gamescope and will boot straight into gamemode/big picture mode without the DE loaded, saving resources. There's lower level stuff as well, like a modified kernel that makes things faster, kmods for AMD APUs so you can adjust the TDP properly, scripts for setting up things like Sunshine easily. It's also immutable, which is great for gaming because if anything breaks on an update, you can easily reboot back into the previous version in minutes and get to gaming without eating limited gaming time troubleshooting or downgrading stuff.

I have it installed on one of the original Lenovo Legion Go's and it makes it indistinguishable from a Steam Deck in function. Even with SteamOS getting a wider release now, it still offers a bunch of advantages.