As soon as the amount of computation (gas) on Ethereum exceeds a certain threshold, gas fees begin to rise. The more gas that exceeds the threshold, the faster the gas fees increase.
Higher fees can be caused by factors such as popular decentralized applications (dapps) or non-fungible tokens, periodic increases in trading volume on decentralized exchanges, or large amounts of user activity during peak hours.
Developers on Ethereum should be careful to optimize the usage of their smart contracts before deployment. If many people are using a poorly written smart contract, it will consume more gas and may inadvertently cause network congestion.