Encountered this issue today, data is imported, but Plugin did not run for any of the records. The Plugin runs when creating record using CRM UI or SDK Call.
Well, the cause is that if you check for
context.Depth in your plugin code, the Async job that executes the import will cause the depth at the first plugin pipeline to be 2.
So the solution is just to ignore
context.Depth check during data import and all will be fine.
Cheers – Sy