The Etheruem mining was not so profitable a few weeks ago. But due to the introduction of ZCash, it is more profitable now.
it's because the diff decreased by a lot, from 6 tera so around 4 tera, now, this mean also that there re no more gpu in play, farm are change changing their coin target, so we have plenty of time at this level before new gpu are added and the diff rise again on eveyr coin