> If you prevent such purchases, you eliminate a major factor in creating the value to begin with.
You're basically saying that they wouldn't have made Figma if they'd only been able to sell it for 15 billion.
Same tired argument as the "unless you lower taxes on the wealthiest even more, they'll stop creating jobs!" (Even though the taxes haven't been lower in history than they are right now).
People do stuff even though there are anti-trust laws limiting how many tens of billions they get out of it.
As long as there's insane profits to be made, there'll still be an incentive.
Selling out to the market leader, creating a virtual monopoly that harms the consumers in the long run, isn't the only way to make money on a start-up. Far from it.