Spinning up a lot of nodes with different consensus rules means nothing. They’d just be another Bitcoin fork since the average Bitcoin Core user (and wallet apps that use Bitcoin Core) would ignore blocks from the theoretical BlackRock nodes. They can try to spin up nodes with shitty policies too, but then you’d get into the scenario that orddisrespector did where they wouldn’t be able to stop the flow of data between honest nodes (which miners always have incentives run in order to maximize profit)