It would take years for the difficulty to adapt to a 10 minute block time if the hash power dropped that much, there is a limit per two week adjustment period. More than likely the code would have to be modified to accommodate a rapidly dropping difficulty. See my other post, but that essentially destroys the security of the minority chain.

BTC rich people are on both sides of the debate, expect to see some dumping all around as they make their positions known.

Not years. The difficulty is recalculated every 2016 blocks (14 days)[1].

If one chain has 10% hashing power, for less or equal to 14 days the transactions could take 10 times more to validate. But that's assuming markets aren't correcting miners in the "right" direction in the meantime. Who wants to waste electricity on undervalued coins?

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Considering most of BTCs have been mined at the time bitcoin core had no competition; I'd say BTC rich people would tend to side with them. Because of emotional attachment, economic ties, and most importantly the dumb but very real reason of software maintenance.

[1] https://en.bitcoin.it/wiki/Mining

But if blocks are being produced at 10% of the expected rate, it will take 14*10=140 days before the difficulty is recalculated.

If you're hard-forking, you can increase the recalculation rate for a few first new blocks. You can even recalculate every block for, say, 1000 or 5000 blocks .

But that wouldn't work for the 'victim chain' of the fork. In this case the idea is that 90% of the miners fork, while 10% remain on the original version.

I don't know if non-miners also check the difficulty or difficulty calculations, but if they do, even the minority chain can't fork without affecting existing users.

In that case everyone would need to fork in which case you're back to square one: what to do with the users that can't or don't want to fork. And if you need to fork anyway, it makes little sense to go with the minority chain.

Realistically, what will happen if mining power moves to an alternative chain but Bitcoins are still what is traded at exchanges, is that miners will move back very quickly. The first one to move will gain the most economically, so game theory dictates the move back will be swift.

In the end, miners mine what people buy. It's that simple.

Any speculation as to what happens if all miners move as one, motivated by ideology instead of economics, is just that.

Mining is centralised enough that large voting blocks already exist, so there is no telling right now which side will win. If the ETH/ETC split is anything to go by, both chaons will survive but only one is going to suceed

That's not true. If not enough people are mining the core chain, then it will be attacked, and your money will be stole due to double spend attacks.

You can't steal with a double spend. At worst you can send a transaction and then later undo it. But that would require the dishonest party to work together with or be the hostile miner.

I'm pretty sure the backlash against both the hostile miner and all of Bitcoin combined would not be worth it, except in a Joker 'Let's burn all this cash' kind of way.

The worst a majority can do, is to create a new longest chain without any transactions. But in that case the transactions would still exist and can be mined again later (and supplanted again later).

But that would require a miner to want to spend resources to hurt the minority fork.

If the minority fork is big enough to be a threat, that would require a lot of 'majority' miners to work together to pull off this attack, which would lead to a tragedy of the commons situation. Any majority miner who doesn't participate in the attack would gain.

If the minority fork is small enough to be a toy for a single miner, it still doesn't make sense to put in the still substantial effort.

Just look at the Ethereum fork. Afaik there have been no shenanigans pulled of by a majority miner on the minority fork, even though it's only about 10% of the size.