That's plausible, and perhaps what Mr Zuckerberg had in mind?
But investors, or at least their opinion aggregated via the share price, had a different opinion at the time.
(Investors are often happy to bet on speculative things, as long as they have a positive expected value.)
I see it them taking a risk and while I thought it was a silly idea, I applaud them for trying. It's hard to imagine Google taking a risk like this, which is the crux of this post and these threads.
I always saw it more as priming the market. Throw out this idea, with the apparent weight of Meta behind it, and see how the market jumps on it (or not). If it goes well, Meta as initiator can easily ensure they stay in the lead, gobble up startups and such.