Forbes answered this question in July: more inexperienced travelers who are unfamiliar with the "rules of the road" when flying, and more travelers unwilling to comply with the mask mandate. The article goes on to add:
The biggest societal reason for violence on airplanes may be because we see more violence everywhere, with seemingly no consequences. Daily news headline scenes of people looting stores, burning down buildings, and rioting when they want to make their point. Entertainment in movies and games is often brutal and uses violence to get others to accept their point of view. As violence is normalized in these ways, it is not surprising that this would be transferred into an aircraft cabin. Blame guns, poor schools, poor family structure, inequitable wealth, or anything else, but violence is increasing and airlines are part of society and part of this trend.
https://www.forbes.com/sites/benbald...h=426c1c2210d6