This is normal. In any study on human subjects, any adverse effect (AE) must be investigated by a third party physician and a determination made as to whether the AE happened due to the patient's baseline health or due to the study drug. If the patient was given placebo, they would always come to the conclusion that the AE was unrelated to the study drug, but this investigation is carried out for patients in the experimental group. The determination is common. For example, if you're giving patients a topic antifungal for foot fungus or something and the patient develops a stroke, it's likely unrelated simply due to how the antifungals work and the fact the medication was giving topically and not systemically.

That said, Pfizer (and most others) made a key assumption early on: that the spike protein itself was not harmful. That assumption may not be true, based on newer understanding about the physiology of the system upon which it works. The spike protein binding to the ACE2 receptor in endothelial (the inside layer of arteries) tissue has a pro-inflammatory and pro-thrombotic effect, which is why we see microclotting with so many COVID patients. Giving the protein artificially as part of a vaccine would cause the same state if it, too, bound the ACE2 receptor. I'm not certain that this was appreciated when the data was being evaluated - so investigators would've missed the connection.

As for the corruption insinuation, I personally know professors and colleagues who have served as peer reviewers for things like this. They take the role seriously and impartiality, even brutal honesty, is very much part of the ethic when doing this type of work. They are, after all, the final check on "new science." If they make mistakes, journals won't hire them as future peer reviewers either. I do believe some people could be corrupt, but I'd have to see proof before I start believing this was intentional rather than an omission due to simple lack of knowledge from the scientific community as a whole.