I join everyone else in this mystery. Certainly the intent was to kill Frankie, so it wouldn't make any difference to Frankie if Michael Corleone or Hyman Roth killed him. It could make sense if the Rosato Brothers reported that Michael had betrayed Frankie and blamed him for the hit in Tahoe, thus giving them a leg up on chiseling his territory, and perhaps turning Cicci.

"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"

"I stood in the courtroom like a fool."

"I am Constanza: Lord of the idiots."