Ethereum offers a lot more than bitcoin as a blockchain. Bitcoin is limited to basically conducting transactions, Ethereum offers smart contracts allowing it to actually store data which is a plus in its favour

Bitcoin only gets pushed up because it has the name that people can recognise. People investing do not know about Ethereum or other coins. They only know bitocoin so that is what they buy. As we move ahead in time that will change. People will see bitcoin and be able to compare it to so many more as their names become more recognisable