Although Fernando Alonso might say that he made his decision to quit F1 "months ago", I'll bet my autographed copy of Jim Clark at the Wheel that he almost certainly made up his mind only when Renault told him they weren't interested.
In other words, the second-biggest name in F1 would be racing in 2019 if only some of the power-brokers had found the time to stop munching their lunches in dark-windowed motorhomes and for once done something useful.
I note that Fernando has thanked Chase Carey of Liberty for trying to persuade him not to leave F1. I don't doubt that Carey used his best endeavours - but trying to convince Fernando to spend another year in the midfield with McLaren is very different from getting your hands dirty and brokering a deal for him to drive the lead, factory Renault.