60GB in version store in short amount of time, allow snapshot isolation is disabled
What other types of activity could use so much version store so fast?


If the instance was acting as a readable secondary replica for an availability group, then snapshot will be used for read queries against that database - regardless of the settings or specific isolation levels requested.  If there are a lot of data changes on the primary for that AG database, or really long running transactions, then the version store can grow very quickly.

Note that this could be a different database and AG from the one where performance issues were occurring - since prior to SQL Server 2019, all user databases share the same version store in tempdb.



Regarding the waits you encountered, one thing I learned recently that's not very intuitive is that hash spills to tempdb incur the SLEEP_TASK wait type.  This shouldn't cause the version store to grow, but it lines up with the disk issues you mentioned with tempdb (disk queue being 1,000, etc).