I have not seen anyone explain Proof-Of-Work this way, so I thought I'd share it here, I'd be curious to know if I'm completely off.
It seems to me that PoW is simply a distributed decentralized source of ticks, a clock, to which data can be "tied"?
The challenge of Proof-Of-Work is a singleton problem (for lack of a better term), i.e. there is only one instance of it in the universe. This means that it is known to every participant, and anyone working on it is affecting the outcome.
Most importantly even if one is participating in complete secrecy until a solution is found, it still affects the outcome.
An analogy might be looking for the largest known prime. You don't need to tell anyone you decided to find one, you only announce when and if you actually find one. Your participation makes finding a solution a possibility, whereas if no one ever looks for the largest prime, it will never be found.
The difficulty algorithm adjusts in such a way that a solution is found on average every 10 minutes. It's a distributed decentralized clock which ticks on average once every 10 minutes. The miners make it possible through their participation, and curiously, miners do not need to tell anyone they are participating, they only need to communicate with others if and when a solution is found.
The clock has an interesting property - you can tie data to its ticks, simply by making the data the input to the SHA. A solved block is nothing more than simply an event that happened exactly at the tick of this clock.
And essentially this is all that Proof-Of-Work does for the blockchain: it provides ticks of a clock, to which events can be tied. Everything else is an "add-on" to this "feature", e.g. using the Merkle tree we can cryptographically record the ordering of the ticks. But without the "PoW clock" none of it would be possible.
Edit: these ticks do come at irregular intervals, so one wouldn't set their watch to it. But that doesn't matter for as long as it is approximately 10 minutes, which it is.
Edit: here is a much more detailed explanation: https://grisha.org/blog/2018/01/23/explaining-proof-of-work/