Sorry, but you don’t get to claim groupthink while ignoring state of Apache when Nginx got released.
Apache was a mess of modules with confusing documentation, an arsenal of foot guns, and generally a PITA to deal with. Nginx was simpler, more performant, and didn’t have the extra complexity that Apache was failing to manage.
My personal first encounter was about hosting PHP applications in a multiuser environment, and god damn was nginx a better tool.
Apache caught up in a few years, but by then people were already solving different problems. Would nginx arrive merely a year later, it would get lost to history, but it arrived exactly when everyone was fed up with Apache just the right amount.
Nowadays, when people choose a web server, they choose one they are comfortable with. With both httpds being mature, that’s the strongest objective factor to influence the choice. It’s not groupthink, it’s a consequence of concrete events.