Why are column store indexes disabled automatically when a database is restored?

I have recently done a server migration where we backed up and restored all the databases from a SQL Server 2012 version to SQL Server 2019. However the restored databases appear to all have their column store indexes disabled by default.

Is this expected behaviour? If so, why?

These are archive databases used for selects only, rebuilding every clustered index is going to take a significant amount of time. Any other options?

(sorry, I asked this in the wrong place here. Can that question be removed?)