it cannot really replace a simple database. it has an integrity guarantee. not in the way that data won't get modified accidentally, but that it won't get modified onesided.

the git version control system also uses a kind of a blockchain structure. git was made by the creator of linux. a major difference is that git does not use proof of work for consensus, I think it just does not use anything for that, other than the web server's access control mechanism.
commits are built on top of a large chain of histories, and the commit ID verifies that the current state and the history of it is the exact same when you checkout that commit ID on any other computer. if you go find in the repository a commit made 3 years ago, and change that commit (this is supported by git but not recommended), either the content or the metadata like time of commit, the whole history after that also need to get rewritten to remain valid, and so all those commits will now have a new commit ID