1. The students who use them. As highlighted by this article theguardian.com/education/2017…, the 'goods' delivered by these scams are often of poor quality - or they take payment & fail to deliver at all. Students can, & do, lose £100s with no redress.
The winners: the essay mills themselves. Unscrupulous scammers, undermining trust and intellectual rigour on a wide scale so they can make a quick buck.