Ethereum became popular as it provided its smart contracts. This is a very convenient platform for creating tokens. Many began to use the platform. Competitors still cannot catch up with etherium.
You're right. That smart contracts have become the key to the popularity of Ethereum.
Other projects can not catch up with him for the reason that ETH has long been a working platform, ranked first in popularity. Therefore, many projects do not see the point of bothering and making their tokens in another network.