Because they have minimal admissions filter and constantly tell students not to give up, to fight imposter syndrome, student testimonials, "this is the toughest thing you'll ever do but it's so worth it."

College is gated by GPA and standardized test scores. You can quibble over the effectiveness and wisdom of this specific gate, but the upside is that mediocre students aren't going to spend a year and $30,000 convincing themselves they're going to major in CS at MIT. At Lambda, students quit their jobs, and take months out of their lives, only to find out 4 months later that programming isn't for them.