Exactly what I was going to write. Path dependency and mental health constrained his choices into an infeasible trajectory, e.g. when the Belgian opportunity.
He wasn't stuck at the airport because of money. He refused to accept new travel documents unless they came with a full British citizenship.
I appreciate your point of view and concerns, but this is not about an institution not delivering according to certain human values that everyone deserves, this is about multiple interactions letting someone stuck and with little options for exiting, the lesson here is that in such extreme cases don't expect human values to appear from out of the blue, and grab any option to escape the Trap.