I would speculate that the reason it didn't work for Watson is the unacknowledged use of Rosalind Franklin's data, with the resulting belief by many that Watson couldn't have done it on his own. The fact that Rosalind died in part due to radiation absorbed during collecting that data adds to the controversy.

Here is a piece of interesting trivia about that. Rosalind Franklin was a true expert on x-ray diffraction. However there are 230 possible space groups. (See http://en.wikipedia.org/wiki/Space_group for more on that.) The x-ray diffraction pattern you see depends on the space group, and so one of the first step is to go through all of the possibilities and identify which one you have, and only then can you really start figuring out what you have. Rosalind Franklin knew about all of them. But by luck Watson's PhD thesis had been on a protein with the exact same set of symmetries that DNA has. As a result he was in a much better position than she to interpret her data.

Yes, Watson is a known jerk who got hit badly by age. That doesn't mean he's wrong when he claims most scientists are stupid. They are.