Most of my relatives had a piano in the house. My decidedly working class parents insisted we learn to play piano. Many of the children of upper class parents go into non-STEM fields, including law. Most do not come from upper class parents. Tl dr I think the original Markdown spec and CommonMark are both significant contributions in their own right!
By the time CommonMark came around, Markdown had already seen viral adoption three of CommonMark's creators are from large companies that were already prominently using Markdown. Gruber's original Markdown spec lacked formality - and that's where CommonMark eventually filled the gaps - but I think that Markdown's focus on user experience over technicality was the key to its success over competing formats and WYSIWYG editors (the real competition).
The Markdown ecosystem wouldn't exist if Markdown hadn't been created in the first place! I'm not confident someone would have made something like Markdown if Markdown was never created: AsciiDoc and reStructuredText came out before Markdown but have not been as successful.
Sure, Gruber didn't allow CommonMark to use the Markdown name, but I feel like that's not a super big deal compared to what he did do. (I didn't always - I actually advocated at the time for CommonMark to respect Gruber's wishes and create their own branding.
