you kinda answered yourself and perhaps suggested the answer, but it's worth saying out loud: they don't want whatsapp to be a chat app. they want it to be the next facebook and they want to smuggle it in a chat app container. if it seems like if it starts working out, I'll be buying Meta stock with disgust.
Why buy stock of something you don't like? Surely you can find other profitable investment options that also then don't support the thing you don't like?
Buying shares in a company supports the company financially only in very limited contexts (e.g. IPO). Buying shares primarily benefits you as an investor.
Buying shares in a company doesn’t benefit its operations, like making a product, directly. Hence, buying shares != support company’s products, however counterintuitive that feels.
