You have conflicting terms here. How did Jordan conquer Palestinian land when they were not at war with Palestine? It is illegal to annex occupied territory so Jordan's attempt was not valid. The West Bank remained Palestinian land. Did Israel win Palestinian land from Jordan? No, it was not Jordan's land to lose.
Unless you are talking about private property rights, there is no such thing as Palestinian land. The land Jordan captured was land that had been abandoned by the UN when it ended the Mandate in the Partition resolution and at that time, Jordan had as much right to the land as anyone else, and Israel and Jordan have settled their differences arising from the earlier wars so Israel now is the only country with a legitimate claim to the land.
There is no rational basis in history, logic or law for the Palestinians to claim the land is theirs. However, just as Israel has been willing to barter land it captured in the earlier wars for peace with Egypt, Syria and Jordan, so Israel has offered to give some of this land to the Palestinians in return for peace, but there is no political entity among the Palestinian leaderships that can credibly offer peace to Israel on any terms. That is why the status quo is the only viable option for Israel and the Palestinians for the foreseeable future.