Git repos are still decentralized. It's just Github was failing, the thing centralized and synced to. The point of Git being decentralized is, being able to take any of the Git repo copies of the current working developer, and host it on a Github alternative. Meaning the code and project did not get lost because of Github. It's not that such an outage wouldn't be a problem, it's just such an outage is still a problem that can be solved and not a showstopper in the longrun.

Even if Github suddenly cease to exist, out of nowhere, everyone who has a repo copy can setup such a server and work on it as nothing was happened (minus the Github features and hopefully nobody uses the Github app). I believe this is not the case with SVN. If the main repo gets corrupted or destroyed, then its an unsolvable problem. Unless you have a backup. And on Git everyone working on the project has basically a backup.

In short, Git itself works offline. But if you are dependent on Github and its features and applications, then it becomes a problem. So I don't know why SVN is mentioned as the savior here.