The pretty obvious reason in my opinion: Ethereum's fees have been quite high for a while, and Binance Smart Chain(BSC)'s fees are drastically lower. And yes, BSC is like magnitudes more centralized than Ethereum, but it comes to show how a lot of people don't care that much if a certain project is decentralization or not as long as they can make their bets on certain tokens.
The explanation is really that simple, a great deal of people do not care about decentralization and over the years I have seen people arguing that it is in fact a disadvantage, it is as if they do not seem to realize that if bitcoin was centralized then it would have been eliminated by governments long ago, and since people have that kind of thinking then there is no surprise that a coin that is heavily centralized like binance is now third in terms of market cap and soon enough it could become the second behind bitcoin only.
The last time I check decentralization of cryptocurrency is only the number one priority within the crypto community because we know the importance of it and the majority of people that sees centralization as a blessing instead of a curse are those that only study trading and other means of crypto investment just to make a profit but they barely study the concept of Bitcoin and the vision Satoshi had when/after he creates Bitcoin.