On the other hand, they are just numbers. (bitcoins) You can double the bitcoin count, their value will stay the same for 2x coins. So what is the problem?
Think about this, they are just numbers.
the miners maybe, if the revenue of their whole mining farm will turn to dust with the next future halving, and with the possibility of bitcoin not growing as intended if this happen, maybe they could force to leave the already unprofitable block reward for a longer time by increasing the limit
basically a modify of the controlled supply, with the right consensus it can be made
If they do this everyone will dump their coins in panic, so what do they have to win by doing that?
As OP said, killing the hardcap wouldn't be Bitcoin anymore, it would be some derivative coin that isn't Bitcoin. Bitcoin = 21 million maxcap, is a core principle.