The strength of BTC lies on the community or masses at large (decentralized) and decentralization means that BTC is everywhere and held by many or anyone around the globe and it's not centered at one place and nobody or group of persons can fight what's everywhere (decentralized) and who tries to fight what is everywhere like BTC will just be like one who tries to challenge his God (Creator) Who is the only living Supreme Being and yet invisible that happens to be everywhere to a wrestling contest and will surely end up loosing.
Please it's just an opinion, you can as well drop your thoughts, opinions, corrections, comments etc let's continue learning. Thank you.
Saying that because BTC is not held by a single individual or entity, that it is held by different people in the different part of the world is the reason behind the decentralization is not entire correct. I say so because coins like BNB is also owned by different people in the world. There's no coin that is owned by only one person.
When we talk about decentralization, we should look at the security method of the coin, the codes, the decision making and lots more.
Looks like you are confused, the price of the coin doesn't affect the chance of a 51% attack, it would affect if the coin were Pos like ETH where some one who holds 51% of the coins can do de attack with staking, but in bitcoin and Pos coins the attack comes from the miners.