Herodias is the subject of this phrase and "she" is a metonym as she wants someone else to execute John. AT: "she wanted someone to kill him, but she could not have him killed" (See: [[rc://en/ta/man/translate/figs-metonymy]])
These two clauses can be linked differently to show more clearly why Herod feared John. AT: "for Herod feared John because he knew" (See: [[rc://en/ta/man/translate/writing-connectingwords]])