Tom didn't win the passing title in 2002, he led the NFL in passing TD's... he also threw the most INT's of his entire career, had the third most fumbles of his career and had one of the worst completion percentages and QB Ratings of his career.
He was far from being the Tom we saw later. Charlie Weis was taking the training wheels off Tom at that point and was allowing him to let it fly because he wanted him to work through his mistakes.
The rest of the team wasn't good either, so the combination of these things was a bad situation... far more than schedule alone.