Git almost qualifies, but it has no automatic conflict resolution mechanism. Imagine how you would program a bank using git as a database. You would put each account balance in its own file and install a hook that checks that no money is created out of thin air. Commits are transactions. Everything kind of works, but how would you prevent double spends in such a system? Double spends are like divergent branches so presumably someone will need to step in and perform a merge. But this someone then becomes a point of centralization, thereby disqualifying git as a blockchain ;)

Git solves a different problem. Look up state machine replication, and then think about the case where some portion of the participants (max 1/3) are malicious. In git how do you deal where there is no central 'trusted repo' to push to, and a malicious participant sends a commit to some subset of participants but not to others (i.e. equivocates)?