The only thing Ubuntu did differently at the time was having a very simple website with a single download button and sending free CDs for free to anyone asking for it which was a big deal when nobody had decent internet connection. Or you'd need to buy magazine offering installation CDs. But the thing is, every single family has an enthusiast cousin, uncle, who in the early 2000's ordereds tenths of CDs from ubuntu for free and gave them out to anyone pulling his hair out of because of an MS windows issue. All that made ubuntu a bit different from Debian like unity, upstart and now snap, only appeared years later after Ubuntu had that reputation of easy distro for beginner.
And this is what really put ubuntu in the limelight and the default goto distro for every new linux user. It was just the most advertised distro, with the simpler website, a general color palette that made it easily recognizable and a nice slogan borrowed from the meaning of its name in Nguni's languages.