Yeah, he probably just liquidated and got diluted over time. Twitter is 15 years old after all and he had a bunch of cofounders. It just makes me think of Saylor's 23.70% stake of Microstrategy which is 20 years old (but also has a much tinier market cap). According to Wikipedia he "controls" 70% of the shares ... but there's no source for that number afaict and it's probably wrong.