Crypto runs on Ethereum because it is a decentralized platform that runs smart contracts. These smart contracts are what allow for the creation of decentralized applications (dapps). These dapps can be used for a variety of purposes, such as creating a decentralized exchange or a gaming platform. Ethereum is also unique in that it allows for the creation of tokenized assets.
These assets can be used to represent anything, from a currency to a piece of property. This makes Ethereum a versatile platform for creating new types of crypto assets.