Thing is, the Houthis (and the people backing them) would attack targets of convenience regardless. The mess in Israel is just the current justification. If the US and everyone else stopped all support for Israel today and Israel became a restored (and entire free of non-Muslims/Arabs) Palestine by the end of the month? The Houthis would resume attacking targets, with new reasons for it, before April rolled around. Because the goal is to secure power by killing (or threatening to) enough people that nobody will resist giving them whatever they demand. And, of course, having gotten what they want through such means once will just encourage them to keep going on the evidence that it works.