Why would an entire race disappear?

Hi, I'm fairly new to DM'ing, and trying to create a world with some homebrew lore, and looking for inspiration.

So in a campaign I'm planning, at the very beginning my players will obtain an ancient artifact that will pretty much work as a McGuffin that everyone wants, and everything revolves around it. The artifact will be a tablet with ancient writings that talk about a forgotten race, that lived in this world millenias ago, but then disappeared, leaving almost no lore about them behind. They were advanced and powerful, basically demigods, as they were born from the spark of creation itself. During the campaign players will investigate what the artifact is, decipher what's written on it and discover the lore of said forgotten race. But now I have to figure out why they exactly disappeared.

I have a couple of ideas like a massive conflict resulting in drastic measures (think Tine War style) or some magical anomalies causing them to become corrupt and thus first demons were born, or even thought of leaving it unexplained and let it become a myth that only has a few theories but none proven right. I'd love to hear your ideas about that.