Blackrock, the US Govt, and Bitcoin

I haven't read into the BTC whitepaper in a long time, so bare with me. I know this will have many logical gaps, but the aim is to get people thinking.

My understanding of Bitcoin - and how it works - is that what makes it so secure to attacks and hacks is it's decentralized nature. As I understand it, in order to control Bitcoin, alter transactions, etc. you would need to control > 50% of the network (aka a 51% attack).

Let's assume that Blackrock is aligned with the US government - which seems to be the case. Let's also assume they have cooperation with the SEC. With these partnerships, if they were to systematically begin to influence mining companies, shut down rival exchanges, and accumulate massive amounts of Bitcoin... is it possible that BlackRock could effectively begin to render the decentralization of Bitcoin m00t - while gaining domination over the blockchain?

I know this sounds far-fetched, and I don't normally consider myself a conspiracy theorist, but with this sudden change of tune in the SEC and BlackRock's entrance into this race, I don't FOR A SECOND believe Larry Fink believes in Bitcoin.

Is the aim here to simply make it virtually impossible (or extremely difficult) to acquire and hold Bitcoin without having BlackRock do it for you - effectively making them the holder? It does seem suspicious to me this is happening as many on-ramps for Fiat -> Bitcoin are disappearing...