Jupiter Is Smaller Than Jupiter, Is It So Small?

Jupiter is where we would expect it to be, given how we expect that it formed. So why would we suspect that it had moved at any point? Jupiter's probablye sitting right there in the spot where you can make the biggest planet. But the question remains, like, why is mars so little? What happened to make mars so tiny? And it's not just mars. The asteroid belt is also kind o like, we don't really understand how it formed the way it did. These are the things that have puzzled scientists for a long time.