AIPAC is not even the top spending PAC in the US. f.e. National Association of Relators contributes nearly twice as much as AIPAC.
If Palestinian cause had any kind of support outside of a few jihadists in Dearborn and some ivy league college students looking to rebel against their rich daddies, a powerful PAC that champions Palestinian cause and spends large sums to influence politicians would have existed already.
Here’s a hint why that hasn’t happened and it’s not complicated – everybody hates you.