Mr. Mueller has obtained a flurry of subpoenas to compel witnesses to testify before a grand jury, lawyers and witnesses say, sometimes before his prosecutors have taken the customary first step of interviewing them.

Being compelled to show up in front of a court before being interviewed? Oh my, I have heard that is unpossible in anglosaxon jurisdictions. I do hope they flee that country and camp out in an embassy somewhere else. </snark>

With the snark out of the way, here is the parts I think is relevant.

Tactics:
With a Picked Lock and a Threatened Indictment, Mueller's Inquiry Sets a Tone - The New York Times

"They are setting a tone. It's important early on to strike terror in the hearts of people in Washington, or else you will be rolled," said Solomon L. Wisenberg, who was deputy independent counsel in the investigation that led to the impeachment trial of President Bill Clinton in 1999. "You want people saying to themselves, `Man, I had better tell these guys the truth.'"

With a Picked Lock and a Threatened Indictment, Mueller's Inquiry Sets a Tone - The New York Times

"They seem to be pursuing this more aggressively, taking a much harder line, than you'd expect to see in a typical white-collar case," said Jimmy Gurulé, a Notre Dame law professor and former federal prosecutor. "This is more consistent with how you'd go after an organized crime syndicate."

Scope:
With a Picked Lock and a Threatened Indictment, Mueller's Inquiry Sets a Tone - The New York Times

[Mueller] appears to be taking a broad view of his mandate: examining not just the Russian disruption campaign and whether any of Mr. Trump's associates assisted in the effort, but also any financial entanglements with Russians going back several years. He is also investigating whether Mr. Trump tried to obstruct justice when he fired James B. Comey, the F.B.I. director.

While Trump showed clearly that he is willing to pardon just about anyone by pardoning Arpaio, the probability that Mueller will find some dirt through emails and bank accounts is extremely high even if Trump associates doesn't cast blame on their current or former boss. You don't get stinking rich by obeying the law.