Ethereum mining is a significant industry. The total industry revenue was $18 billion in 2021, more than bitcoin mining’s $17 billion.
If everything goes according to the plan, the merge will take place on Wednesday evening/Thursday morning and replace ETH miners with validators. ETH miners have invested billions of dollars in GPU mining rigs. These rigs can’t mine bitcoin, so the soon-to-be-obsolete ETH miners are looking for other tasks to direct their rigs’ computing power to.