The benefit is that many third-party services and many users don't want to have to trust a centralized auth provider. The blockchain provides redundancy and security guarantees which don't require trusting company employees. Not to mention the financial incentives which are associated with being an early adopter of a blockchain project and the network effects which come from that.

I'm convinced that decentralized communities will eventually corrupt and destroy all centralized services and agencies by manipulating their employees and members... Because they can. People will always find a way to create new problems to make themselves necessary. In these political games, decentralized anonymous communities have the upper hand. Unlike centralized projects, you can't corrupt decentralized projects. What can be corrupted, will be corrupted.

To understand why it's the future, you need to look at the big picture. You're assuming that centralized auth providers are secure and trustworthy. This is not going to be true in the future. Trust in institutions and organizations has been eroding and will continue to erode.