Pointing out that there are competitors doesn't change that their presence doesn't overthrow the monoculture. After all, Gecko was around for a long time and Firefox did become very popular very quickly after version 2; but realistically, it took until Apple put WebKit on iOS for any real dents to be made.
Also, I think Konqueror still uses KHTML by default. I don't know if Konqueror tracks WebKit, but I think they're rather different these days.
KHTML was the only community driven browser engine and thank god for it. God knows what the browse landscape would've been without it.
That's the monoculture.
Edit: didn't realise you were responding to someone refuting what you had said, haha. so basically we agree, I just thought you were someone else.