maybe the card just crashed, if it doesn't have temperature monitoring I don't think it would have protection,

this reminds me of my Radeon 9100 (8500LE), at some point I removed the cooler, but it was originally "glued", it left behind a mess which I like an idiot made it worse by scratching the GPU with a screwdriver, to make things better I had no way of installing the heatsink again, so I decided to use the 8500LE without any heatsink, just the scratched thing and a mess of thermal paste, I think I had some 80mm fan near it at least, and it worked perfectly fine on windows, and I even played Halo with it, it would artifact and crash at the default clocks, but underclocking it made it run stable !

oh well, after that I took some sandpaper and made the GPU surface smooth ish again, bought some Vantec cooler, overclocked to 310Mhz and business as usual 🤣

going by my experience you can crash old Radeons from overheating without necessarily killing them at least....

I think at the end of the day all that you can do is make sure it's properly cooled now and test it.

if the crash is related to some protection or it simply failing to work well enough for the driver (I think that's it), I don't know, but it sure doesn't thermal throttle and so on like modern stuff.

You can expect your GPU to be degraded already, resulting in reduced remaining lifespan.
Possibly it is dead tomorrow already.

For my part, I made the experience that many graphics cards have fans that like to die, and the cards die inevitably soon too.
I liked to use Nvidia Quadro XGL cards, and these fan had to be disassembled and lubed regularly, because when it got too slow, the card got very hot, and died soon, no matter the fact that cooling worked fine again after maintenance.

For this reason I got used to use fanless graphics cards. Normal external ventilators are usually of better quality, and can be exchanged much easier.