Seems like you could have made that same bet by just buying BTC with that money and doing twice as good.

Up to a point; once it was over $12k or so, it was cheaper to mine them than to buy them. But yeah, I guess in retrospect I could have just dumped ~$450k into buying BTC when it was at $3,000 and made 3x what I ended up making, but there were other considerations for why I did it at the time. The mining was co-located with my cannabis grow/operations, and in many ways the mining was started secondary to that, even though the mining ended up being a little more profitable over the life of the facility

I dunno, probably only if you don't count for human psychology. If they bought N BTC and tried to held them, would they still hold them when they double in value? What about increasing 10-fold?

Compared to doing some work to getting 1 BTC per month, which you can then individually decide what to do with, instead of a lump sum you could cash out at any moment.

I mined in 2014 with free electricity and that was true even then. That's with hindsight though, the mining reward is more predictable than that market price would increase (more than) equivalently.