Data in a blockchain is hashed by sha256 so when the data is modified by bad actors so is the hash, this is what secures a blockchain so why is POW necessary? I understand the double spending problem but couldn’t you just include time stamps in that hash, so where would POW come into play?
POW is a consensus algorithm, it helps multiple actors/nodes/parties to agree on what should be the actual state of the system that everyone will consider valid. So it simply solves a different problem than linking blocks to each other in a blockchain. There are actually many different other consensus algorithms like Proof of Stake for example.