They don't. Vast majority don't "get rich", especially not grinding out in a sh**ty Singapore law firm charging a fraction of what international firms charge, even as an equity partner.

Most lawyers who are "rich" are so because their family was rich to begin with. And many lawyers come from such backgrounds. Nothing shortcuts the process of amassing of wealth as much as inheriting a large chunk of assets from your parents. Certainly not grinding it out as a partner.