Unfortunately it started to be taken seriously, at least by academics who went on to infect an industry. I shit you not when I tell you the Software Project Management module I took at university described Agile as “Waterfall but done much faster” back in 2010/2011.
It's a lot like "GOTO considered harmful" where everyone knows the title changed by von Neumann but not the actual discussion (both by Dijkstra and the response by Knuth)
