ethereum is gaining momentum because it has being advertised a lot, getting pumped by those holding lots of money and the 72 million premine, and also because of the large number of ICOs on it.

it has higher fees compared to 90% of the altcoins. and its network is congested to the point where you have to pay $4 fees to get your transaction processed at times.
it has higher costs for creating a smart contract compared to all the other similar smart contract platforms.
smart contracts are also possible with bitcoin so does with at least 20 other better platforms with so much less cost.

the chances are very low but i no longer underestimate the power of the centralized banks behind an altcoin pump.