“why did Muller unseal the indictments and make them public”
What’s the significance of sealing versus unsealing as it applies to this situation?
Mueller knows there's no way he can actually get these Russians into a courtroom. Consequently, there 's no reason why he could not have waited on the indictments until after the summit meeting. The announcement of these indictments a few days before President Trump's meeting with Putin was designed to sabotage the summit and try to make President Trump as uncomfortable as possible going into the meeting.