There were solutions before blockchain, especially in the field of Byzantine fault tolerance. The original Byzantine Generals paper was from 1982, and practical algorithms existed before Bitcoin. For example: PBFT - Practical Byzantine Fault Tolerance - published in 1999.
https://css.csail.mit.edu/6.824/2014/papers/castro-practical...
Blockchain solved a different version of the problem: how can a large, open, permissionless network reach agreement when anyone can join and nobody has a fixed identity?
Classic BFT is like a committee of known people voting, where the system survives some liars.
Blockchain is like letting strangers on the internet vote, but making votes costly enough that cheating becomes economically difficult.
> The lack of CS knowledge on this board is pretty staggering sometimes.
Right!?