Earlier quoted context omitted.
>All that matters is the valid history with the largest weight (longest chain rule in PoW). No, that exactly the believe that comes from BTCs implementation and while it may be true for BTC its completely irrelevant for other systems. Imagine there is a room full of people all have a paper with the exact same transactions in order on it. Now a new person joins and copies someones paper and then verifies all Tx. Ok, n…
>So why even copy the chain first he could just start asking for the hash of the whole thing and if they all have the same there is no point to copy the chain. Well if I control enough nodes I can send you fake hashes (51% attack).
The type of attack you are thinking of is called a Sybil Attack [1].