Over half of the Bitcoin Network went offline in 48 hours

This is a misleading (and I would venture to say false) headline: the hashrate is not the size of the p2p network.

It is however significant for split network attacks. If a malicious actor where to control >50 of hash rate double spending becomes a thing.

Not as decentralized as one is expected to believe indeed.

How much more difficult would it be to extend this further so that the entire Bitcoin network goes offline?

This sounds promising for any groups looking to shut down the system and stop the energy usage.

hopefully, the rest of the network can also be brought down