It is definitely a big concern.
If countries or powerful people accumulate too much power, it defeats the purpose of bitcoin. The real purpose was to empower poor and weaker sections of the society. But if powerful have most of the bitcoin, they will become powerful and weaker section will suffer more. There is an additional concern that rich might be accumulating with different identities.
No. The real purpose was to grant self custody. The ability not to rely on a third party after the financial crisis of 2008.
Hence Decentralization
The purpose of Bitcoin is defeated when it is used through a third party or requires a third party
Like one is using a Bank.
Indeed, there hasn’t been a shift from its original purpose which is as a p2p not because this isn’t acceptable or within its system but it’s rather limited due to adoption. Adoption that is gradually coming to be and possibly, faster than we would have hoped given how many nations are picking the pace toward having some form of Bitcoin reserves.
I would not concern myself with these nations and corporations with huge holdings, aside from having to have these holdings, coming together to form an effective alliance would always be a problem.