I think the answer is very clear. Ethereum is underperforming because right now all the attention is on Bitcoin. We must remember Trump's words and promises (the move has turned out well) about Bitcoin and cryptocurrencies, and they are being effective at least in terms of popularity and increase in economic value. Now, many more companies and private investors are investing in cryptocurrencies than a few months ago, but they only have eyes for Bitcoin, hence the rest of the coins/tokens barely increase in value, or do so minimally. I don't think it's a cause for concern, when Bitcoin goes down again (some corrections will be necessary) the rest of the market will possibly grow again to some extent.