> What else _is_ there to learn about this that people are looking for?

This is where it gets a bit interesting. While Merkle Trees are great for ensuring, immutability, most cryptocurrencies need more than just that. They need to have a way for records to be inserted into this immutable ledger and an incentive to keep adding records to the ledger. This is where Proof of Work and mining rewards come into play, and this is where a lot of altcoins (non-Bitcoin cryptos) have a lot of different opinions. A decent amount of work has also been put into making sure that there isn't an incentive for a miner to mine on two different chains (and cause the ledger to fork) and other concerns.

Based on my cursory understanding of the topic, The Merkle tree has been around for a while, but Satoshi figured out how to use that to achieve decentralization, and consensus building. If you ask me, that's quite revolutionary. Yes, the blockchain is just a gigantic DAG, but adding and deleting nodes on the graph is where the crux of the matter is I guess. I am starting to understand the logic from a currency perspective. Still trying to understand how the same translates to smart contracts.

It's also the same thing with the git commit tree. You see commit IDs change when you rebase because of the parent pointers.