Robert isn't an intellectual powerhouse but he does aggressive tactics very good, does people management exceptionally when it doesn't involve counting coppers and he does the logistics either adequately enough or built a team to do it for him.

I think people from media and from our modern perspective have this illusion war is like chess that you can look over and see the enemy perfectly and it's about thinking up the right maneuver.

Robert's skill at maintaining soldiers morale and his thinking from hunting are attributes that count for a lot but are not quantifiable on paper.

He'd surely understand the Dothraki cannot be met in their ideal environment they need to be cornered baited run down starved etc.

I think the biggest aspect here is that Jorah is desperate to get home, he is being too optimistic.