My first thought was that maybe fan culture and atmosphere has changed, which would have a more noticeable effect in the higher leagues, because lower leagues are still hilarious [1][2]. But the home advantage seems to affect all leagues the same, so I am probably wrong.

[1] https://www.youtube.com/shorts/KXmv7VK_110

[2] https://www.youtube.com/shorts/aTHc9Xinb6U (uncensored: https://www.tiktok.com/@bunch_amateurs/video/733659771889629... )

but the efforts to stamp out hooliganism have been harsh pretty much at all levels, in the English game. I think that's an overlooked item. It would be good to compare trends across different leagues, where there was little or no equivalent effort.