The Mossad wouldn’t take out Assad. They know that while he’s a Son of a Bitch, he keeps his people in line.
I actually agree. We will never know for sure how many times Israel and leaders of countries who “hate” Israel have had back channel discussions and agreements. It is that nebulous area between the “public” face and the “private” face. All nations do it, and sometimes, in the case of Obama visiting Israel, things can only be talked about leader to leader because phone calls, written notes, various electronic communications, and intermediaries or underlings won’t suffice.