I certainly hope that last bit where Captain Galaxy gets a letter from little Sam wasn't
met to imply that that is how Sam got his
theory in the first place. Why? Because Captain
Galaxy was dead at this point in the original
timeline and thus never read Sam's letter.

Pogo Effect!

Besides, it was Sam-in-this-Leap that gave Captain Galaxy the rest of that theory! I was laughing through this whole episode, but part of my nitpicking mind was screaming, "Paradoxes! Ahh! No! Sam, shut UP!"

Both Sam and Al had that look of paradoxical
credulity on their faces when Moe read the
letter from little Sammy Beckett from Indiana
at the end.

Probably the real reason for this leap was for
Sam to help correct Moe's time travel theory so
that AFTER Moe's life was saved he would answer
the letter from Sammy Beckett that would give
Sammy the kernel of the idea that Sam would
start to work on in college so that he would
come up with the Quantum Leap theory of time
travel that would lead to the creation of Project
Quantum Leap so that Sam would prematurely enter
the Accerlation Chamber and begin leaping around
his lifetime so that he would end up leaping into
Kenny so that he would save Moe's life and in the
process help him refine his time travel theory so
that Moe could answer the letter that would give
little Sammy Beckett the idea that time travel
was possible in the first place...or as Captain
Janeway would say:"Time paradoxes give me a
headache!"