Not that obvious, how do you coordinate people from several of teams working on it?

IBM managed to coordinate several hundred people on a single software product for decades on end.

Even Microsoft managed to do so for multiple products while also stack ranking the teams.

And I doubt there's a single service, even payments, that's as technically complex as Excel.

Do you really have 4,000 teams working on payments?

And I'd agree with the other child comment that the monolith can always be broken into separate components which are owned by different teams.