I'm not suggesting that this is the sole reason, but have you considered the possibility that the US supports Israel in part because it is a white-majority nation of largely European ancestry among Arab states? Especially considering the circumstances that led to its creation. I am more and more convinced lately that this plays a part, though it may be small.
However, what you mention is clearly happening too. It's likely a variety of factors, but I would agree that money is a big motivator. AIPAC is certainly able to achieve a high level of autonomy, so that would point to it having tacit endorsement/approval from the US political establishment and that's more than likely from legalized bribes.