As the leading Muslim country in the world, Saudi Arabia has a duty and responsibility to stand up for the rights of the Palestinian people, who are facing genocide in Gaza. Additionally, Saudi Arabia also stands firm on its position that a cease-fire must be reached in Lebanon. Hopefully, the incoming Trump administration will work with its allies in the region to end this terrible war.
Israel cannot take its Arab allies for granted and must act wisely regarding how it conducts itself in this war. The relationships Israel has formed with countries like Jordan, Egypt, and Saudi Arabia are critical to Israel's strategic position in the region, and thus some sort of resolution to the Palestinian question must be achieved.
The only reason bin Salman is talking tough about Israel is because he is afraid of losing his legitimacy with the Saudi people, especially the youth. The crown prince reportedly told the US that he doesn't care about Palestine or Palestinians, but is worried about internal backlash. Saudi Arabia's support of Palestine is rhetorical only.