The Ludicrously Simple Answer:
After weeks of investigation by enthusiasts pouring over thousands of these cryptic videos, investigators discovered that "Webdriver" might refer to automated testing software. Then Italian blogger Soggetto Ventuno uncovered the fact that the YouTube account may be associated with Google's Zurich office, and that there were other channels across the Internet with similar videos. Not long after he posted links to said videos, they were ominously deleted.
But then the Webdriver Torso pattern began to change. One video included the first verbal message to ever come from the channel -- "Matei is highly intelligent" -- before cutting to a few seconds of footage of the Eiffel Tower. Then this happened:
Yep, whoever was behind Webdriver Torso totally Rickrolled the conspiracy theory-spouting masses. Engadget finally closed the case once and for all when they approached Google's Zurich office for an official statement:
We're never gonna give you uploading that's slow or loses video quality, and we're never gonna let you down by playing YouTube in poor video quality. That's why we're always running tests like Webdriver Torso.
There's still debate as to whether they told a below-average Internet joke, or an above-average Swiss one.