Why Stafford before Armstrong?

Here's a question which has been bothering me for awhile.

Why did Tom Stafford command an Apollo mission before Neil Armstrong?

In Gemini, the New-Nine command order (the order in which New-Nine
astronauts commanded missions) was: McDivitt, Borman, Armstrong, Stafford,
Young, Conrad, Lovell.

But in Apollo, New-Nine commanded in this order: Borman, McDivitt, Stafford,
Armstrong, Conrad, Lovell. We all understand why McDivitt and Borman were
switched, of course (due to the LEM not being ready, etc.), But I have never
found an explanation as to why Stafford commanded a mission ahead of
Armstrong.

Theory: After the Apollo 1 fire, it became clear to Slayton, and possibly
all of the astronauts, that Armstrong was in line for the moon landing due
to the perceived (or actual) flight rotation at that time and to the
perceived number of mission-types, which, I believe at that time may have
been *4*.

Possibly, before the Apollo 1 fire, Slayton had already designated *at
least* the first 6 Apollo commanders as: Grissom, Schirra, McDivitt, Borman,
Armstrong, Stafford, thus maintaining, among the New-Nine, the previous
Gemini command order (and, I believe, ignoring the Cooper wild-card due to
unpredictability).

Keeping in mind that, prior to the fire, Owen Maynard's alphabetical mission
sequence had not yet been devised, really, and that, at that time the only
reasonably-clearly-defined manned Apollo mission-types were the two
low-Earth-orbit missions, which would later be designated as the C and D
missions, it is, nevertheless reasonably to assume that, as far as bringing
the program up to the point of having completed the Big Moon Landing, only
*2* other manned Apollo missions-types were envisioned, which would later
turn out to be the missions designated as F and G.

Now, it can be argued that, ultimately, not only did it take five manned
Apollo missions to bring us up to the completed Moon landing, but even five
mission-types were originally envisioned as missions-types A through G
(post-fire), nevertheless, there were never really more than *four* manned
Apollo mission-types:

C: Test CSM in LEO.
D: Test CSM and LEM in LOE.
F: Test LOR.
G: Land on the Moon.

So why were there five missions? And five planned mission types? Well, as we
all know, mission E was scrubbed (or radically altered), yet Borman, Lovell,
and Anders went around the Moon on Christmas 1968 in a mission which I have
seen as variously designated C prime, E prime, Or F prime, since in
fulfilled mission objectives for each (mostly E and F). This was done, not
to fulfill any direct space-program objectives, but to beat the Russians to
the Moon, which was a clear political objective which played a major part in
justifying the existence of the program in the eyes of the public.

So, in essence, as I believe most people involved in the Apollo program saw
it in January, 1967, there were only *4* real manned Apollo mission-types.

So here is my guess at the sequence of events: After the fire Slayton sees
that his list of Apollo commanders is now Schirra, McDivitt, Borman,
Armstrong, etc, and since he *assumes* that four manned missions will result
in a Moon landing, he sees that Armstrong is in line for the landing, and
this knowledge leaks out and becomes generally known by the astronauts.

Then Maynard decides five manned missions are necessary to produce a moon
landing, thus effectively bumping Armstrong from the coveted first landing
spot. Since this sort of bump is not something that the astronauts would
generally accept as valid, Slayton decides to *switch* Armstrong and
Stafford in the flight rotation order, most likely with the knowledge and
approval of both.

I'm probably way off, but I still can't figure out why Stafford and
Armstrong seem to have been switched.