I’m curious: who is operating these bots and to what end? Someone is willing to spend a (admittedly quite small) amount of money in the form of tokens to create this nonsense. Why do any of this?

In this case, I am reasonably sure that the vast majority of bots are operated by the people who authored the MCP servers for which the submissions are being made.

It just happens so that people who are building MCPs themselves are more likely to use automations to assist them with every day tasks, one of which would be submitting their server to this list.