The articles I’ve read make it sound as though air stewards asked man in question if he could move seats so they could place the body in his row, and the man just scooched over to the window seat to make room. Which sounds like an odd thing to do, rather than say “are there any seats anywhere else, not sure I want to sit next to a dead body for the rest of the flight”, though maybe just the shock rendering him unable to articulate that.
It’s unfortunate, but things happen. I’d like to think the airline offered some sort of voucher or air points etc to thank him for being a good sport, but they can’t prevent situations like this.