Not all wall street firms end up success, many were bankrupt, but you won't hear the bankrupt story. The higher the leverage, the higher the bankruptcy risk. And for sure, real estate business has the highest leverage across industries IIRC. What I want to say is, you don't always need leverage.
The OP is just surely talking about the top of all what's happening with those people in the wall street but didn't totally get what they've been through. Not all people will be successful if they loan some money because I believe it takes a right knowledge and experience on how to manage an investment.
You can be wealthy from side hustle without borrowing any money. The key is reinvesting your excess income, not from debt.
Yes, it's true and this is what the Chinese have been doing why they are always successful in their business. And for those who can afford to lose with a higher leverage they are the ones who are ready to risk in order to gain a name in the industry of business.