Learning is the most important. School provides a structured environment for learning, as well as accreditation. I personally find self-learning far more efficient than school. But at the same time having a degree changes people’s perception of you and if other people have better perceptions of you, that can make the social aspects of doing business easier.
You have to look at the conflating variables as well. People who go to good universities are from richer backgrounds on average and this means they have more support and fewer problems at the very early stages of building a business.
I worked in the trades and now I’m doing part-time work to pay my bills while improving my programming skills. I just signed up to go back to university and I find that much of it is just slogging through stuff without much immediate benefit, and perhaps dubious long-term benefit. Certain types of universities may provide you with support or at least a good environment for building a business, but I would guess those are hard to get into.
Conflating variable: income. People who attend big universities are more likely to be well-off and have more resources to spare than the average American. Most of those dropouts are from nicer backgrounds, very rarely from places like Appalachia, inner cities, the projects, the rez, etc.
Rich people get degrees. Rich people get lots of money from daddy to build their startups. They are more likely to succeed. They can afford to sit on their ass and program up wild ideas for years at a time, or hire someone to do it for them. They can save time by getting some dude on instacart to go get their groceries for them. Or they don’t have to cook cuz they use doordash. They can afford subscriptions to time-saving services for things like accounting and other business-related stuff. When something breaks they don’t have to fix it themselves. They have more time to focus on building their business, and more money to throw into the money pit.
If you’re from a trailer park and go get a degree from Central Cornfield County Community College then you’re likely to be flat broke and unemployed by the time you graduate. Then you might get a mediocre job and can spend the next 5 years saving up money to start a business. You can’t afford to take too many risks and lose much so you go for something with fewer capital costs and higher labor costs. You slog through for a decade and it can potentially become moderately successful.