Rs do a lot of phases and investigations and investigations of investigations and inquiries and theses and speeches and (add here).
Mueller just indicts.
This is the way a white collar criminal investigation goes.
First you complete the investigation and gather all the evidence
Once you have the evidence in hand, you question the suspects
In this cases perjury is always a concern and it’s much easier to get to the truth when the guy getting questioned does not know what evidence you have against them
Looks like these guys are serious