Your research was maybe too quick. You probably didn’t see Poppy standing outside the Book Depository, see where he was that day “officially,” where he spoke, where he said he spoke. See where he SAYS he was, on the occasions he even remembers. See how he got two different alibis going, one that included a clever tip to the authorities, man was he clever, and one that included his wife Quaker Oats man, who was pressed into helping him alibi, in writing. By the way, no one has evidence he COMMITTED murder. Just evidence that he was right there and apparently REALLY didn’t want to have that known.
I just read carefully the biographical information about Prescott Bush in Wikipedia. WOW!!! Nothing good can follow from that family tree.