Obviously the US government is sending an endless supply of arms to Israel without conditions because doing so serves its purposes.
The question that you need to ask is how it serves its purposes - how is it that the US government benefits by enabling Israel's Palestinian genocide.
My theory, also supported by other US government actions in the Middle East (such as the Iraq war) is that the US government's overall goal in the Middle East is destabilization.
And that stands to reason, since the Middle East's wealth administered by stable and progressive governments rather than reactionary autocracies could he a threat to western hegemony.
Or more simply, a Middle East consumed by strife can't be stable, and thus can't invest sufficient time and resources into being a serious player on the world stage, since too much of its time and resources is diverted into dealing with internal strife, or pissed away by the dysfunctional governments that have come to power as a result of of the strife.
And Israel, and specifically the overt violence and oppression and now genocide failing to hide behind a shabby mask of "defense" and "security" in which Israel continues to engage, is key to that strife.
If you look at US foreign policy in the Middle East through that lens - asking yourself, at every turn, how does this accord with the presumption that the broad goal of the US government in the Middle East is destabilization, then a lot of things that don't make sense otherwise suddenly do.
