Peak Lenin occurred in 1967. One year before Soviet tanks invaded Czechoslovakia to back the Soviet version of socialism by force. It needed to be supported by force: people no longer believed socialism.
Mao peaked in 1970. By the end of the same decade China started to dismantle his legacy. Although Mao is still nominally revered in China, nobody wants the Maoist socialism to come back.
Socialism peaked in 1976. Here's why:
The term 'welfare state', however, peaked relatively recently, in 1999.
The human race will be better off when all of these terms become history.