The only surprise to my way of thinking is that the Israelis were never able to successfully assassinate him. Have no idea how accurate the movie, "Munich" was but I'm amazed that the Mossad never had the will, or ability, or timing to send him to Hell (or "Paradise" depending on your point of view) long before his "Appointed Time"...
They certainly had the ability and likely, the will. It was "political considerations" on the part of Israel's democratically elected government that retrained them.