Q: .fseventsd = 130GB

.fseventsd is the file system for notifying spotlight changes  but that size does seem excessive.

you may want to trash the spotlight index and reindex that volume.

Spotlight: How to re-index folders or volumes - Apple Support

Description (per a web search):

.fseventsd is a log file of "(F)ile (S)ystem (EVENTS), logged by the a (D)aemon". Basically there is a monitoring background process ("daemon") on OS/X called fsevents which it notices whenever files are created, modified, or deleted.

So assuming it is indeed nothing more than an OS controlled log file, such a large size indicates a runaway process that is causing the OS to create the same entry (or a few of them) over and over, causing the file to grow to an unusual size.

If nothing else, they should all be log files that can be safely deleted. Make a full system backup first, then remove the contents of the folder.

Assuming the description I found is correct, then it matches up with my guess that a daemon for some process was going nuts and making oodles of log entries. What one that was/is might be able to be determined by reading some of the logs if it starts filling up again.