Marriage records are often public. But usually two people don’t stop using a dating app and get married the next day. They will date for months or years after. And that info is not so easy to get.

As far as data brokers I would imagine it’s possible to get info on an individual if you want to. You can even determine someone’s location based on data brokers info. But dating apps will want info on millions of people, which will be messy and hard to do.