The approval for that drug was a huge error but you’re incorrectly conflating that limited, conditional approval with the far more rigorous normal process. The FDA basically said that the manufacturer has 10 years to show a clinical benefit because the drug was shown to accomplish its purpose (reducing amyloid plaques) with an acceptable level of side effects — and that’s not completely off the timeframe needed to measure a slower disease like Alzheimer’s. In contrast, the Pfizer vaccine has been shown to be highly effective at producing positive clinical outcomes and has been administered to massive populations with very infrequent side-effects which are far below the risks of the disease.

I think it was a big mistake not to keep that as some kind of trial but my primary reason for that is because it encourages faulty conflations like yours. The message we should take from this is that the problem was NOT following the standard process rather than drawing any conclusions about the process which wasn’t followed.