The ceo of Starbucks is Howard Schultz one of the long time people associated with Starbucks. This is his third time being CEO including the period that made Starbucks a household name and when it went public. He’s not at all associated with Vanguard or Blackrock.
The next CEO was chosen by the board in a very public CEO search. Laxman Narasimhan has the pedigree you’d expect from someone picked for that role including being a ceo of a big company and a long stretch at Pepsi.
Perhaps you can be specific about what you think Vanguard or Blackrock did as part of this process that caused a three time ceo & founder of Starbucks to be chosen as the interim and then followed by what appears to be a highly qualified candidate?