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
I am sorry, but I am not wrong.
First of all, neither Western Union, nor the IMF can do anything that remotely resembles printing money. Any entity that can "print money" freely would do just that, and buy up assets for their own benefit, not use that printed money to harm a perceived competitor of theirs.
Your scenario is very sensational, however it is simply not realistic.
If an entity wanted to harm Bitcoin, they would not ned to bother blocking a proposed network improvement, they could simply buy up sufficient mining equipment to be able to prevent transactions from confirming, and/or cause the orphan rate to be uncomfortably high, especially by orphaning long chains of blocks, and/or abandoning the long standing principle that the first seen transaction is the valid transaction, and that conflicting transactions should be ignored, subject to certain limitations. This entity could harm Bitcoin even if the PoW is changed, it would simply be more expensive, although if the PoW is changed for this reason, it is likely that confidence in Bitcoin would have likely declined sufficiently so that not many people would use it anymore.
It is not possible for an entity to both mine bitcoin to harm Bitcoin and mine bitcoin that results in profit (from that mining activity). If the miners are collectively harming the network, then presumably, the price of bitcoin would decline, rather substantially, and the time it takes for a miner to recoup his investment in mining equipment is a long time, with higher amounts of revenues at the beginning of a miners' useful life.