> Ubuntu became the most used because they were the first to really dumb down the install process.

That is an urban myth relayed by people who weren't even using Ubuntu in its early days.

Other distros were as easy to install as Ubuntu even before Ubuntu was founded. Besides Ubuntu was using the then experimental debian installer you could already use with a regular debian. They just shipped it on the default CD image earlier than debian did.

What they did to be on top was using Mark shuttleworth's money to ship an insane amount of free install CDs to anyone asking for them which meant that for a small period of time, when most people were on dial up internet ISDN and shitty ADSL, Ubuntu went suddently to be the number one distro installed. A friend, family member or coworker was curious about Linux? You'd hand him one of the fifty Ubuntu CDs you had lying around. I know I was one of those handing out CDs left and right. It was a time when to get an install CD without broadband you'd have to buy a magazine, and you didn't get to choose which distro was featured each month, a book or a boxset (not available everywhere). Later all those many early ubuntu adopters became ubuntu evangelists.

But bar a few exceptions like slackware, debian with the default vanilla installer or gentoo, there was nothing particular about the ubuntu install experience compared to other distros. Mandrake, Corel Linux ans Xandrows for example provided super easy install experience even before Ubuntu became a thing.

I'd largely forgotten about Mandrake/Mandriva, did they offer a live environment with installer as a GUI application? I'd tried to install Mandrake probably closer to the year 2000 and it certainly did not, but, there's a 4 year gap there that's a blind spot for me pre-Ubuntu.

Never messed with Corel as it wasn't around long, so can't speak for that one.

Focusing more on say, 2005ish, can you think of other examples?

While Ubuntu did build on Debian testing/unstable, they did invest in building the GUI on top of everything, paying salaries for a few Debian developers.

With a very slim team (I am guessing 15-30 in the first couple of years), they picked Python as the go to language and invested heavily in development tooling making it possible for them to innovate and pivot quickly. Yes, they grew to a mid size company of 500-1000 over time, but also expanded into many different areas.

Perhaps one can also make a case for them effectively starting and killing a number of projects akin to Google, except they usually made them open source, and some live on as volunteer efforts (eg. ubuntu touch).