Even a decade ago I was seeing obvious cheating when I was TAing classes. International students would hand in an essay with clearly broken english, then follow that up with essays with complex, well written english that was obviously not in their "voice" or even in the same intellectual ballpark as exhibited in the in-person class and discussions. Even pre-internet, essay writing was widely regarded as " library stenography" by students.

The meat of the matter really comes down to the professors and how they approach the exams. Generalized essay prompts are hilariously easy to cheat on; complex hyper specific prompts that extend on something specifically discussed in the class are far harder. On-line classes, by their "mass distributional" nature (ie, save money by making them reusable) are almost by definition far more generalized than you would want.