You're oddly being downvoted for that. Not being paid nearly as highly in tech in general, detracts from how much money is in the ecosystem for doing start-ups.
If you can sock back a retirement working for big tech for 10-12 years (counting equity), it frees you up massively to do whatever you like, whether funding as an angel, or self-funding your own start-ups. It's not uncommon for people you know in tech in Silicon Valley to pitch in on early small funding rounds if you've started something new and are rounding up some early funds. Multiply that wide process by the scale of the US tech industry - at the small and large ends - and all the wealth that has been created in it over the past 30 years.
1.3 million software developers with a median salary of $110,000 is a lot of money just from the software developer worker bees every year (save N% per year of that pile, now it's available for investment in one form or another; and that's ignoring the equity value they're yielding).
Europeans are a lot worse at capitalism, in general, than Americans. Partly because we're not required to be. Western Europeans are more or less born into a massive insurance scheme that will bail you out whenever the going gets tough. This is mostly good, IMO, but not without cost.
Also, there's less of an entrepreneurial mindset in europe. DO a good job, get paid, work life balance. Very different set of goals from america