These are all generalizations, and there are plenty of exceptions, but:
1. Religious Christian conservatives tend to support Israel because they believe that Israel's existence is foretold in the Book of Revelation and is part of God's plan. Jesus will return to Israel and the final battle will be fought there outside Jerusalem, the Rapture, etc. (The fact that modern Israel was founded mainly by atheists and secularists is unknown or ignored.)
2.Many progressives, not just here but around the world, see Israel as the last example of western Imperialism in the developing world- basically the white man having his way over the poor natives who can't hope to compete with the white man's technological superiority. When I was growing up, Apartheid South Africa was the #1 world villain in this regard and Israel #2. But since 1992 Israel has held the bad guy role all to themselves. (The fact that Israel was established as an independence movement against a white colonial power- England- and that during the War of Independence and for many years afterward the Israelis were technologically inferior to their Arab opponents- is unknown or ignored.)
3. American non-religious conservatives tend to be extremely attracted to the "tough" attitude of the Israelis- the fact that they don't seem to take any crap, that they are ready to respond militarily at any moment, that almost every man and woman owns a gun, etc. Conservatives would like America to be this way as well. ( The fact that Israel was established as a socialist nation based on communes- kibbutzes- and that both of the major political parties in Israel are economically far to the left of the most progressive Democrats in this country- is unknown or ignored.)