On 5 Live a few weeks ago, they had a guy from the FA on and he basically said this happens every few years. One happens, gets attention (especially if there’s an incident like Billy Sharp’s)and then a bunch of copy cat incidents happen. Suddenly every end of season event - a comeback, a relegation 6 pointer, PL survival, cup or play off win, title win etc - All have to have a pitch invasion so the fans can show they care as much as all the other fans.
Then everyone goes away over summer, forgets about it,and it all stops for a few years.
He gave the impression that the FA wasn’t that concerned, they’d seen it all before.