A possible reason for the ending of the series is that Sam changed Al at the end by setting it up so his wife and he are reunited after he gets back from being a POW in the war.
A even more in depth possibility might be that the time travel project wasn't really started by Sam, but by Al. It's possible that Al had a twin (this was never mentioned one way, or the other), but that would explain the "Evil Leaper" that Sam ran into a couple of times.
How it could have went was that Al and, his brother had worked on the program, his brother had sent himself the same way that Sam did, but they didn't expect memory loss, and Al's brother started to do the things that Sam would later have to undo. A leap could leave a electrical signature that Ziggy's equipment could pick up, and that's how it knew where to send Sam.
At the end, he chooses Al over going home, but the Al who is now reunited with his wife might never have started the program in the first place. Therefore the Sam that we all new would vanish himself because he now doesn't exist, but a Sam with his wife. might now exist because of the time line change.
A even more in depth possibility might be that the time travel project wasn't really started by Sam, but by Al. It's possible that Al had a twin (this was never mentioned one way, or the other), but that would explain the "Evil Leaper" that Sam ran into a couple of times.
How it could have went was that Al and, his brother had worked on the program, his brother had sent himself the same way that Sam did, but they didn't expect memory loss, and Al's brother started to do the things that Sam would later have to undo. A leap could leave a electrical signature that Ziggy's equipment could pick up, and that's how it knew where to send Sam.
At the end, he chooses Al over going home, but the Al who is now reunited with his wife might never have started the program in the first place. Therefore the Sam that we all new would vanish himself because he now doesn't exist, but a Sam with his wife. might now exist because of the time line change.