It happens because, in spite of Roon blaming hardware problems for a corrupted library, I suspect there is also at least one software bug that causes problems.
I’m betting that Roon software doesn’t take any checkpoints before undertaking a critical update on their database, and so if a problem occurs there is no way to back out (or even recognize) an incomplete operation.
Only an opinion.
Back up your library frequently and because of an inadequacy in Roon’s Backup logic, I recommend backing up to several locations on several schedules and with different retention periods.