Some kind of patch management or vulnerability detection software that removed it instead of replacing it? (Or attempted a replacement but only made it to removal?) Other than that, I’d guess some do-gooder who saw an older version of Java and had to remove it for safety.
If this is Windows, you should be able to hit up the event logs and search them for the uninstallation event, or just all things Java. It might not lead you directly to the culprit, but it might give you an idea.