While I don't agree with the reddit valuation to begin with...

that is actually how the stock market "should" work? Reddit is a company that, at its core, produces data to sell to other companies. If other companies choose to (say they are not going to) use that data, then the value of reddit drops. That is literally supply and demand.

If Stanley's Sprockets' sprockets are a vital part of iphones then Stanley's Sprockets is going to be a very valuable company. If Apple changes to the other dude's product, Stanley's Sprockets has now lost a lot of value.