As the box says "Divi is more than just a WordPress theme, it's a completely new website building platform that replaces the standard WordPress post editor with a vastly superior visual editor. It can be enjoyed by design professionals and newcomers alike, giving you the power to create spectacular designs with surprising ease and efficiency." Its why we have enjoyed using Divi to power all our customers websites over the last several years.
Ease of use
Ability to easily use CSS or not to change the look and feel.
Customisation of Divi WordPress themes
Divi Community and support that is behind the product