At a glance, I don't understand why white would offer a draw from this position. He appears to be winning if he just stacks pressure on the c-file. He is up a pawn with a better position. Admittedly my diagram might not have best play/be perfect tactically, but the basic idea appears to be clearly winning.
Even though white is up a pawn at the moment, that advantage doesn't really translate into anything pratical, since he also has doubled pawns on the d-file, isolated b-pawn, backwards e-pawn and a Knight vs Bishop situation.
And as far as just stacking pressure on the c-file, I do not think that it would be so simple. Black can just trade off the Knight and apply some pressure of his own:
I offered my opponent a draw in the above game, and he chose to accept it. But my question is, was it actually a sound draw offer, or did one side have a large enough positional advantage to pull off the win?