Seasoned readers (or even those only on the sub for a few months) know that, but the influx of WSB readers is coming from average reddit users who are here for the get-rich-quick and "stick it to wall street"
theme the GME squeeze has ignited. They'll be the ones disappointed and holding the bag once everyone, including WSB veterans, have cashed out.
They care because Wall St. fucked over the entire planet in 2008 and these guys are sat around, bored, probably with an extra stimulus lying around, and have been told they can destroy a few hedge funds via GME.
I don't know how realistic that is, but the message is certainly powerful.