The probability may be low but the number of attempts allowed is unlimited (barring time / energy / other obligations). So one can keep trying until something sticks. The important part is to keep trying.
It's also a convenient way to justify not saving enough.
I've watched fairly successful business owners make this mistake many times - they were making 400K or 500K (in some cases, millions) a year off a business, but not saving anything because they still expected it to grow a lot larger. If it fails to grow, then end up either broke or in debt.
It's inherent to entrepreneurs that they believe in the big future payoff more than average, but that's also a big blind spot for financial planning.
Your examples showcase the pitfalls of bad planning and not the probability of business success. Success doesn't absolve one of the responsibility to plan, but being someone who did succeed can open up additional doors and options for the said plan.
The entire problem is that most folks grossly overestimate their probability of future success, even over a lifetime.
(Not to mention likely done a lot of damage to your health and relationships, if you spend a career trying to finally achieve a big outcome... there are non-financial costs to taking bigger risks that we often fail to assess.)
As for probabilities, spending 10 hours per week, thinking, and iterating on side projects, over the course of 10-15 years can bring a sustainable $10-15k monthly pre-tax income if done well. (I define well to be build stuff people want, focus on your customer, etc) If one's time horizon is smaller or income needs are larger, then there are other leverage points that can be used.