That's what exploration looks like; mutation plus selection. I think you know this but consider exploration willful, perhaps?

> mutations are random

Kind of. Mutation rate of our dna is "managed" by the dna/chromosomes/genes to reduce the rate in critical areas.

Yes, but those mutations are part of why evolution works. Through random mutations, every possible way of doing something is explored. If something is beneficial, organisms thrive. If it's not beneficial, organisms die. The same is for whole species. If a species was using some niche to their advantage and the niche disappeared, the species will die. But that niche (nook) was explored.