Fabregas obviously didn't overly annoy Wengie when leaving since we made sure we got that first refusal clause in his contract. In the immediate aftermath of the transfer Wengie also said that Cesc may return one day. That's not something he usually says when players leave.
I can totally understand we didn't exercise our first refusal since we have Özil in that position. However, if the plan is to play Özil wide, then Fabregas would surely have been the best possible transfer we could have completed this window at a very decent price. My opinion anyway.