It has everything to do with Flash. Flash was the only reliable way to record via webcam and have it instantly available.Citation needed. I don't know of ANY remotely popular flash vlog recording service of the time. Not to mention that vlogs in general never got that popular, period.
You have to respect that YT is a community, one with a pretty significant voice. Type in "sopa", "war in iraq", or "arab spring" and see how many cat videos you get.
YT is not a community at all. It has tens of millions of extremely diverse members. You can find any kind of shit in YT, from democratic, to republican, to anarchistic, to pro-nazi, to various nationalisms, to kittens, to porn, to full length movies, to ads, to high culture, to fart jokes, ... What part seems like a specific community with a voice to you? It's just the assemblage of millions of individual tastes and opinions.
The fact you can find things about sopa, war in iraq, arab spring etc does not mean anything of the sort of YT being a "community" with a "voice".
It's like finding emails and blog posts about such issues: of course you will, there are millions of bloggers, thousands of them are bound to write about the issues of the day.