In PoS, why does a block header need to be signed by the miner?

I am reading the following article about PoS http://earlz.net/view/2017/07/27/1904/the-missing-explanation-of-proof-of-stake-version In this article, the author says The block hash must be signed by the public key in the staking transaction’s second vout Why is this necessary? I understand that in PoW there is no need to sign the block because there is no transaction that consumes…

What are some potential scenarios that a state actor can harm bitcoin if they control more than 51% of the hashing power?

As reported recently, China controls more than 51% of the hashing power and just in one province in China controls 54%. Assuming China has bad intentions and forces all these mining operators to collude to harm the Bitcoin network. What are some of the potential scenarios to dethrone bitcoin from the #1 spot? From my…