The linked article says he was arrested on a charge of attempted GBH but no doubt that would / could change

I've just watched the video back a few times and the only thing that I can think is that he runs past a man and then pushes the woman, now the media narrative I picked up was almost that he runs past the man but once past he can then push her without it being seen / witnessed however -
The man is walking to the side of the pavement whereas the woman is walking basically smack bang down the middle.
I'm wondering if he was pissed off that she was right in the middle and getting in his way which made him angry

Now it's a fairly wide pavement and personally I don't see any issue with where she was walking as he could easily have adjusted his course slightly and gone either side of her.
I will admit it is annoying when out walking / running / cycling on a pathway when people get in your way especially when the path is narrower but OK for 2 people to pass but someone is in the middle so you can't go either left or right of them

I actually had this yesterday walking behind someone who was walking slowly, I held back as we did need to cross over a couple of side roads which were at the junction onto a main road and there were cars waiting to pull out.
The man was well aware of my presence but once we were past the traffic he then walked right down the middle of the path and seemed to make himself as big as possible swinging his arms either side of him
All he had to do was move to the left or right (as I would have done to let the faster person past) and I did think to myself that he was being an ignorant twat, anyway I ended up stepping onto the grass to get past him, not a massive issue as it wasn't wet and muddy but at no point was I considering pushing him out of the way especially towards the busy road