What does Vitalik means by "smart contracts where next person to interact with gets a substantial reward"?

This quote is from the the article In Defense of Bitcoin Maximalism, posted on Vitalik's blog:

Ethereum's battle with miner-extractable value (MEV) is an excellent example of this problem appearing in practice. It's very easy in Ethereum to build applications where the next person to interact with some contract gets a substantial reward, causing transactors and miners to fight over it, and contributing greatly to network centralization risk and requiring complicated workarounds. In Bitcoin, building such systemically risky applications is hard, in large part because Bitcoin lacks rich statefulness and focuses on the simple (and MEV-free) use case of just being money.

I don't understand the sentence in bold.

Can someone explain me exactly what Vitalik is referring to?

I feel like it is a way to develop a kind of "useless" logic that the builder could exploit to earn more money. But don't really get the point, neither the link with risk of centralization.

​

Thanks for your help!