Isn’t mining and transactions separate? Sure you need to have online participants, but they don’t have to actively mine, right?

You can generate transactions but ultimately transactions are validated and written in the blockchain by miners. Mining is essentially a way to select voters based on their ability to solve puzzles, ensuring that if you are selected once you have no particular advantage next time. Without miners this whole system doesn’t work.

No, mining is exactly what makes transactions go through, computing the next result in chain, certifying that the transaction happened.