He had lost his mother 36 hours earlier.
Most people in that situation will have privacy and space to process what’s just happened to them, perhaps surrounded by a few friends or family. He, however, has had to fly back to London the day after her death, meet people outside Buckingham Palace, speak to the Prime Minister - which can hardly have been a pleasurable experience - film a broadcast to the nation, and doubtless had many other meetings with staff, and calls with other Prime Ministers in Australia, NZ and so on.
After perhaps 3-4 hours sleep, he then had to go through what looked like a fairly tedious ceremony the following morning, again in front of a room of people he’d probably rather prefer weren’t there. In those circumstances, can anybody on here really say that they wouldn’t - perhaps for a second or two - react to something in a way that’s slightly out of character, or make a very moderate fuss out of something that wouldn’t usually rile you?
I think that any rational person, with an ounce of empathy, would cut him a bit of slack. The children on Twitter, however, are incapable of doing that, while a number of people on here rush to embarrass themselves by declaring him a c**t. It really is incredible how some people behave.