miners as a whole have very real incentives to do what is best for Bitcoin, including when deciding if they will signal for a particular fork/proposal, and if/when there is a serious threat to their ability to continue mining bitcoin (such as a serious threat to change the PoW), they have substantial incentives to not act in Bitcon's best interest (they have incentives to act in a way so that they can continue mining bitcoin, even if this means acting in a way that will damage Bitcoin over the long term).
Wrong
If I was an organisation like Western Union or the IMF (who can print fiat money, so it's essentially cost free to them), I would set up a mining farm, sell all the BTC for profit, and block any attempts to upgrade the Bitcoin network. I'd design a hard fork that screws Bitcoin up, and employ loads of trolls to promote it.
Bad actors can and do mine BTC. You're very naive