While rare, this isn't the first time the FDA has deviated from its advisory committee's recommendation. The FDA, understanding the public attention this drug approval would get, has rightly stood by its reasoning, including the life-threatening nature of Alzheimer's, its unmet need for treatment, and the evidence that the drug reduces brain plaques. As with all approved drugs, the FDA has closely monitored its success as it entered the market.
This report is not surprising in the slightest, as the FDA has been engaged in blatant drug approval corruption for a long time. While this may not be widely known, large pharmaceutical companies literally fund the FDA's drug review studies in what's known as its "user fee" program, leading to a never-ending cycle of regulatory capture.