I thought it was related to the number of micro states that are equivalent to a given macro state. So, as the number of particles increase, the temperature increases or the volume increases, there are more possible micro states. That’s why very cold things or very ordered things (crystals) have low entropy, because you can’t readily swap out microstates.

It’s also why a pile of legos is high entropy; you could easily swap legos around and the pile would be indistinguishable. Whereas you can’t do that with a built lego.