Uh, '90s were rife with open right-wing extremism as well. The '80s were also not short of it either. Even the DDR had a living right-wing extremist scene - believe it or not. It does not have anything to do with previous eras of *-wing extremism because both scenes can pretty much coexist and always have, whether one side resurfaces more openly or not depends on people's general views and stances, heck the left-wing extremist '90s RAF was a different one than the '80s or '70s. Same for right-extremists, back then in '90s the average right-wing extremist was a skinhead who dropped out of school after 8th grade and had the mental capacity of a Faxe beer can and fists bigger than brains. These days have passed and it has entered the stage where it's become acceptable at burgeoise levels.
Left-wing extremists have left the stage of wanting to establish anarcho-communism and defeat capitalism that way, nowadays they just want to smash and burn capitalism whenever since globalism and the long-gone iron curtain with Big Brother Sovietunion gone too have pretty much reduced their original goals to rubble and weakened them, whereas it strengthened the far right with the resurgence of identary and nationalist movements. In fact both kinds of extremism are a lot more scary than before. Back then right-wingers would never even think of attacking the police, the new branch of right-wing extremists however does, back then left-wingers would not seek wide-scale destruction, the new branch however does. Attacking eachother's politicians has become the norm again too, just like at times of Weimar Republic.