I think it dropped because of their strength in primary care. I believe a large portion of their grads go into FM for underprivileged areas which greatly detracts from their ability to write grants/conduct research as an academic.
It seems the whole point of the article was to judge the schools based on the graduates they produce rather than the faculty that exist at the school. No one is denying UCSF as a powerhouse research institution, they just have a broader focus than some of the other more purely research-focused schools which only crank out academics.