I'm a little surprised that after last season that we didn't get some interest. But then, thanks to Costa, the season didn't end too well for him.
Hazard is a wonderful player. But he can't do what Dembele does anymore than Dembele can do what he does. Dembele's forte is winning, holding, and distributing the ball from midfield. As has been said by many, including De Bruyne, he's so strong you simply cannot shake him off the ball. He also has far more skill than he's credited with.
Also, he's 30 next year, which would dampen interest from many.