It would make non-Twitter social media providers like Mastodon, Pleroma, Pixelfed and others more competetive, since they offer a better experience not motivated by corporate interests and can explore more sustainable and ethical business models. Twitter adopting ActivityPub would also be incredible validation of everything we've been working towards and lead to more platforms joining the decentralized social web and more exciting and innovative projects being created in this space.
@Gargron
"Twitter adopting ActivityPub would also be incredible validation of everything we've been working towards "...
Used exactly this argument to someone who was mocking the move of some of us to Mastodon.