This wouldn't shock me. The Pats could've gotten a second round pick for Jimmy G. from any number of teams. I'm sure when trading a QB with talent Belichick most likely ruled out first AFCE, then ruled out AFC. After that he may very well have looked at the NFC west with Seattle, L.A. and Arizona thinking that San Fran would have tough sledding for the foreseeable future and determined that would be a good landing spot for Garoppolo.
Least likely spot for the trade to come back and bite him in the a**.