The networking code, the in-depth blog posts, even the attention to things like preserving mod contracts when introducing breaking changes. The team running Factorio is a great example of a well done gaming project.
There tends to be an automatic assumption that if you didn't succeed then you did something wrong, and that if you did succeed than you did it all right. These two things are less connected than that. There is "luck" involved here (in quotes because it's more complex than the phrase "I got lucky" implies).
To draw any kind of conclusion about whether Factorio was a success because of its execution as a gaming project, we would need to examine a range of other games, successful and unsuccessful, to see how well they executed and whether that caused a matching amount of success.
I'm have more admiration for the fact that they don't have sales. The only way to get a discount is to use a third party discount system like humble monthly.
Sale (people selling stuff): "forza vendite"
sale (discount): "sconto"
Also, not related, but another interesting example:
"free" (open): "aperto"
"free" (price is zero): "gratuito", "gratis"
Doesn't mean that Italian is superior to English. Simply means that in certain languages, words are ambiguous where in others they are not.