Oh, I think Roethlisberger did it.
Regardless, there was an entire SI cover story about how big an a--hole he was, so it's pretty stupid to suggest he got off easy. Heck, he still gets flak for it (and deserves it).
But to be clear, the reason he got off easy was because none of his accusers ever wound up pressing charges. They knew what kind of legal team Roethlisberger could afford.
Darren Sharper doesn't exactly make Roethlisberger money. And while I'm sure he can afford a good legal team, he's facing seven accusations at once Roethlisberger only faced two, and they weren't concurrent.