If you were conspiratorial, it would be as follows…
People know he has a tendency to be very very nervy when under pressure, people know he has a tendency to be edgy when under pressure, people make sure that he is put under pressure and people make sure that no-one is there to act as a buffer.
Most managers have had a tete a tete with some mouthy fan, but they also (vitally) have someone close by to calm them down in the heat of the moment)…to be honest, this seems like something which could easily have been either unreported, avoided or seen AVB ushered into some common sense at the touchline by one of his own staff…none of that happened…
At the end of the day, he is responsible and should've been smarter. But I do think there are forces at work to undermine him, and I hope he discovers the necessary comprehension of the situation/intelligence, to make it through, otherwise it will be costly for him...