The succession planning was non-existant ahead of Fergie's exit. Surely it shouldn't be a surprise that a man of 70+ years thinks about retiring.
The moment Pep left Barca wheels should have been set in motion to accommodate his arrival. He was free and available during most of Fergie's last season.
It's what Bayern did after all, they planned ahead. Worked out okay.
And the excuse that Fergie didn't decide to step down until late into the season doesn't fly. Gill's job is knowing things like that. It was obvious that Fergie would step down if not at the time, then soon. An opportunity like Guardiola should always be sounded out, at that stage.