I'm not forgetting. And I'm not claiming that this promotion was a mistake. I am raising questions about the narrative that the author is telling/selling. Consider how you'll likely not see such a long-winded post from company founders explaining in detail why they chose themselves for their own jobs. They founded a company because they wanted to, and they didn't care whether they had exactly the right experience and qualifications.
The narrative is about slowly making your way up the corporate ranks, gaining experience, working hard, achieving qualifications, and deserving your promotion. The author feels that this kind of story is encouraging, uplifting, that is shows you too can make it to the top, but I actually think it's kind of a disservice, an attitude that can hold people back. The company founders suddenly made it to the top at the very beginning without any of that, without "deserving" anything. If you think you have to "earn" your position, you've already bought into the myth of the hierarchy. The best reason to be ambitious is the realization that the people above you are just as flawed as you are.
If anything, competence is often overlooked in promotions. For example, from the article: "I didn’t get promoted right then (it wasn’t the right time) but we also stopped looking for an external hire." Why wasn't it the right time?