You are right TB. Pentangeli was to be murdered days before Michael was to be murdered. This would throw the Corleone family into chaos, and gratly strengthen the Rosatos and Roth.
It turns out it was Roth's good fortune that Frankie lived, and ratted Michael out.
Once everyone was out of Cuba, Roth obviously learned that Frankie was alive, and it then was very easy for him to place a call to Questadt and let this new plan to destroy MIchael play itself out.
"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."
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