I disagree. Firstly, him doing a bad job in New York doesn't mean he'd do a bad job here. It's a new team in the 2nd season of it's existence in an established league. No manager in the world would be guaranteed success. One of the most successful managers in that league has just failed, so why would anyone else find it easy to win?
Secondly, if he was an assistant to Pep (or Guardiola if you prefer) during a period of success, he could learn from the top man, help integrate the youngsters he has coached, and there would be an easy continuity if he was to eventually take over.
Thirdly, he was doing an excellent job at the EDS, was an extremely popular member of the staff at City with both the established professionals, and the impressionable existing and potential future youth team players.
If he fails at NYCFC and gets sacked, we're losing a major asset from the club.