I'm not going to give him a round of applause like Reddit because I think he was acting with some degree of carelessness and attempting to commit a penalty, but I do think it did occur enough in the context of a consensual sporting activity that it was an accident and not something that should result in civil/criminal liability.
After watching that clip dozens of times, my opinion is the same as that of the deceased victim's aunt's as presented in the article linked by the OP:
Adam Johnson's aunt, Kari Johnson, said in November 2023: "My nephew was 6-feet tall, and whether you lost your balance or not, to have that leg come up that high and do a kicking motion like [Petgrave] did, that is just unacceptable.
"I think the actions were unnecessary. It was just unnecessary. Nobody touched him. I've watched that video hundreds of times."
That I believe that Matt Petgrave intentionally raised his leg, by no accident, and also delivered a kick intentionally. Now, it was not intended to kill, nor even hit the head. But I fully believe that the kick was intentional.
Hence, manslaughter is a perfectly logical thing to investigate(third degree murder):
The unintentional killing of another through an eminently dangerous act committed with a depraved mind and without regard for human life
Now, when I presented this view, I was met with massive downvote campaigns on reddit, etc., but I definitely agree with Kari Johnson, as that's exactly how I saw it. And while many people seemed surprised that manslaughter is even being investigated because it was "pure accident," I replayed that clip countless times and couldn't come up with any other explanation than that he kicked Adam Johnson intentionally.
Now, I'm expecting this to be an unpopular opinion here as well. Which is sad, since I for one would assume that people would be looking for justice for the deceased.
Can I donate to the prosecution so he gets his proper manslaughter charge?
Agreed, I would donate for that if I had the link to do so.