There's a difference between knowing about a topic and delivering 30-45 detailed lectures on it, tailoring it to the learning needs of students, etc. It IS easy to be a bad professor, but it's easy being bad at anything. "Programming is easy. You just learn a few programming languages and then it's all just retyping stuff you already know. Pretty easy way to make good money."
Further, "good money" is a questionable statement. Putting aside the 70% of faculty who are contingent (making $2k-$3k per course), you'll find that most faculty are making in the $40s-$50s. Doesn't sound so bad for a starting job, but then you have to remember that they've been earning nothing for most of their 20s. Keep in mind, they're also working most evenings and weekends (endless grading for some fields), not to mention required service on university committees, being a reviewer for journals, etc.
I love being a professor, but it is not easy money and it's usually extremely stressful until your 40s (at which point it begins to be more like a "normal" job). So yes, a lazy, tenured professor at the "peak" of his or her career may have it really good. But that's not representative of the field and, even then, it usually requires immense sacrifice and stress to get to that point. One might as well say that CEO of start-ups have jobs that aren't stressful because "they're rich and get to order employees around and set their own schedule." Sure ... but that doesn't describe most CEOs and it doesn't give any sense of what it takes to get to the "easy" stage.