It may be that Nxt is in fact 100% secure because >50% of the stake has always been held by a few people such as Marc De Mesel who will defend it against attacks. That doesn't make it decentralized nor does it make the method secure just because Nxt in particular might be.
I guess you have to ask yourself, "How much does decentralization matter if the currency holders are the ones that secure the network?"
It certainly does. The point of cryptocurrency is not Moon. The point is to have a system of enforced rules where all participants are protected not only from outside attackers but from each other.
I never said the point of crypto was only to make money. I think for a lot of the original believers in crypto that was more of a secondary consequence. I understand your point of participants not being protected from each other, but there are very few people who would act to their own detriment.
The point you are missing is that it isn't necessarily to their determent. You're only considering "crash the world" type attacks. If Bitcoin miners 51% attack to prevent increasing the blocksize and drive up fees while maintaining their competitive advantage, they help themselves at the expense of people who want to transact with lower fees. That's just one example that comes to mind, and maybe not the best example regarding PoS but the underlying issues are the same.
Crypto without decentralization is just inefficient fiat (aside from the zero sum trading game aspect).