Decentralization is as much about who is administrating than it is about where and how it is hosted.
With MaaStodon, we centralize hosting, but not administration. Centralization has very valuable perks, like making it much easier for anyone (not only experienced sysadmins) to own a Mastodon instance and participate in the federation, or pooling up resources to share a powerful infrastructure even with small instances. But it becomes a single point of failure: more instances will risk having issues at the same time.
We believe centralization is in small amounts very useful and can help many instances exist in good conditions. MaaStodon doesn't aspire to host all Mastodon instances, we want to make hosting Mastodon instances better and easier. To show that, we support migrating instances in and out of our services at any time, and we will progressively release the software we use under a free license.