Supply and demand. Demand for block space on Ethereum main net is very high. Billions now transact every day on Ethereum DeFi protocols. Like traditional markets, the opportunity be first to hit an arbitrage can be worth millions.

Against that the Ethereum devs are extremely conservative with block space. To maintain decentralization they want consumer hardware to be capable of running a node. Chains like Solana provide a lot more supply of block space by simply cutting out consumer hardware.

This is not typical. This is a deep pockets person using off-chain messaging which went awry. The people gaming the system understand the risks.

From the article, '... the participant attempted to use Flashbots to gain an advantage.'