Twitter has to do everything itself - sales, marketing, customer support. This means that its vision is limited by what the executives can see, and they're going to look at traditional business factors for ideas. The political structure tends toward corporate fiefdoms over time.
Mastodon is leveraging forces from many different directions: first by building towards the existing GNUSocial protocol and its userbase, and then as different communities come in, getting donations of their time and skills to operate instances tailored to their needs. Businesses have angles on this too: for example Japanese art site pixiv made their own instance and client app. The federated model allows some divergence but also the "loose ties" of a common protocol. There is the prospect of embrace-extend-extinguish occurring, but this historically only happens some of the time, and it requires the full pressure of a giant tech firm and all their marketing strength to make it work.
Mastodon is leveraging forces from many different directions: first by building towards the existing GNUSocial protocol and its userbase, and then as different communities come in, getting donations of their time and skills to operate instances tailored to their needs. Businesses have angles on this too: for example Japanese art site pixiv made their own instance and client app. The federated model allows some divergence but also the "loose ties" of a common protocol. There is the prospect of embrace-extend-extinguish occurring, but this historically only happens some of the time, and it requires the full pressure of a giant tech firm and all their marketing strength to make it work.