Although in this case Meta bought companies that were already established and successful.

Google bought Android before it had released products.

Google Maps was purchased, but was Where 2 actually a successful product prior to that?

I feel like you just cherry picked from my examples. YouTube was certainly successful - Google bought them because their own Google Video competitor was a flop. DoubleClick was also obviously huge. Where 2 had a successful product, it just wasn't web based (nor do I think free), so didn't have anywhere near the distribution that Google enabled once the team ported it to run in a browser.