Just looking at shares is over simplistic.

You can't know what other conditions Mullenweg signed in contracts such as shareholders agreements etc.

Typically if you take VC money, the VCs will require the ability to sack the founder and take control, perhaps if particular targets are not met.

I've seen it: an ambitious owner agreed to stretch goals, and the VCs took took over the company from the founder after they had predictably failed to meet the goals.