People are betting that Ethereum will falter in the next bull market, that something shiny and new will take all the spotlight from it. Looking at the ETH charts though, I doubt it.
Who are these people? EOS, TRON, ADA fanatics?
Ethereum has the network effect that most probably, no other altcoin will be able to take from it. "superior" smart contract platforms are present already, but most people aren't interested in that, just like how people aren't interested in coins that provide faster and cheaper transactions than Bitcoin.
EOS and TRON are both inflating all sorts of metrics to point out how many users are active on their platforms, but it's super easy to manipulate metrics on these platforms into oblivion with how transaction fees are either zero or just barely above that. Developers and the wider dapp ecosystem have chosen already, and that choice is Ethereum.