The Ethereum network is the most mature network enabling smart contracts, and it also has the most active development community. The other networks with smart contract development capabilities are either still in beta or in development.
Indeed. And even if the other networks claim that they have lower transaction times, they don't have the level of usage that Ethereum has.
Scalability developments in Ethereum are going well, it seems.
But do not exclude that Ethereum can move from the second place coinmarketcap. It is hard to imagine when a small part of the projects on Ethereum will start, then the network will fall exactly. Perhaps the appcoin has plans to switch to another blockchain in the future.