A bridge is the first step in the “Embrace, Extend, Extinguish” pattern. A Fediverse only works when no one node can dominate all the others. It’s why, even though Meta’s Threads platform was/is actually Federated (in that it uses ActivityPub), everyone defederated from them because it’s a poison pill for the whole network.
For more info on how that eventually happens, this article gives some past examples.
Each time one of these for profit social media platforms fails or gets cancelled or whatever, some portion of the userbase switches to the Fediverse.
My hope is that eventually we will reach a critical mass where that portion makes up a majority of the transfers, at which point we will have successfully dismantled the industry of walled-garden social media.