I don't think like that. Ethereum is always popular, my assumption that there are still many ICO projects that use the ERC-20 platform, and position ETH on the market is number #2. In my opinion, many people sell their Ethereum because:
1. They sell ETH when prices are high to get profit.
2. They panic sell when there is bad news about crypto or exchange hacking.
3. They want to invest their assets in other coins.
4. They sell ETH because need money for urgent needs in a real life.
5. They sell ETH because do not understand price fluctuations.