> Why is Bitcoin made up of back-links to previous blocks? Isn't a block no more than a memoization of a event-sourced log at a point of time? That's just a really badly constructed journaling filesystem.

My understanding is that the chain of blocks, whereby each successor block is dependent on the hash of the previous one, acts as a self contained proof that a huge amount of work went into generating this. The rule that everyone needs to follow then is to simply always trust the longest chain presented to them (or the one that was most difficult to build depending on the amount of solutions at every difficulty.) By only looking at the last block, you lose this consensus mechanism. Not sure exactly how that isn't an issue with PoS though since they aren't verifying with work, and it seems that they can just keep track of the head of the transactions.