UX is broad. This is the main reason why the importance of UX outweighs both SEO and CRO.
The other two reasons get at the heart of the two issues.
- SEO: To rank for search results, you must successfully deliver what the search engines want. In order to do so, you must first achieve an optimal user experience.
- CRO: To gain conversions, you must create a website that is easy and enjoyable for users. This is all about user experience.