the top 20 stakeholders
It's not about targeting the top 20 stakeholders, but top stakeholders who together hold 51% of the voting power.
datacenters or hosting companies can be targeted
That's why I run at least one witness backup node on premise.
And as @trostparadox said, should they take Hive down, we would simply fork it and restart, as we already did.
There are diminishing returns potential to that last ditch mechanism, and I am certain all of us would prefer to prevent losing what resources in infrastructure, stake, and community are endemic to existential forks.