It's entirely political. The miners and related business interests that profit off of bitcoin have a lot of influence and a lot of clear incentives, but any message signed by Satoshi could completely alter the direction of bitcoin.

Check this argument by ChatGPT:

There are several ways that miners could try to convince the Bitcoin community that a change to increase mining rewards would be beneficial.

- They could argue that the change would help to secure the network by providing a stronger incentive for miners to continue participating in the network.

- They could also argue that the change would help to increase the overall adoption and use of Bitcoin, which could lead to an increase in demand for the cryptocurrency and ultimately drive up its value.

I hadn't really considered this before, but I think there's a good chance they'll do something to increase their take-home if bitcoin becomes cheap enough relative to the mining reward that its security becomes threatened. Right now there are lots of people mining bitcoin at a paper loss due to speculation. If they go out of business after a few years, or are forced to sell because "number goes up" doesn't happen, there will be an exodus of mining power, which could then lead to the Bitcoin network being vulnerable to double spend attacks (these have already happened a number of time on networks with less hash power, like Ethereum Classic [not ethereum])

If double spends looked imminent, or started occuring, I think it would make sense to fork to increase the block reward. Of course, bitcoin has forked before and it becomes a political issue. Personally, the big block wars (and subsequent Bitcoin Cash split) was where I got off the Bitcoin train.

But if a fork happened, and the network that didn't adopt the higher block reward started getting 51% attacked, I do think people would move over to the new network (and that would become "bitcoin")

If nobody mines the old fork then users will have to switch.

No, but lets say a the big traditional instances do not accept the non-forked chain. Only the forked one. How good would that chain be for your average new user that is forced to accept transactions on the new chain.