Bitcoin did not break any "technicality". Technically speaking, the chain with most work is to be considered valid. What they did back then was, a bunch of mine

Bitcoin did not break any "technicality". Technically speaking, the chain with most work is to be considered valid. What they did back then was, a bunch of miners got together and created an alternate chain with more work. So it's still technically the correct/longest chain. On the other hand, Ethereum just plain broke the sanctity by basically creating a chain that contains a transaction without a valid signature.