The main issue is that he used heavy machinery for cleanup. If it was by hand it probably wouldn’t have resulted in any legal matter

Yeah, he went way beyond simply removing trash:

The team removed more than 200 bags of rubbish along with branches, thick layers of silt, weeds, discarded household appliances, used needles and even abandoned weapons. Their goal was to restore the natural flow of the water and remove years of accumulated waste.

He basically dug up the entire riverbed. That isn’t something people should just be doing ad-hoc.