The question is, "Why would the writers put the 2 words 'well-regulated'
into the amendment if they did not expect the government, either Federal
or State, to have the ability to well-regulate arms owners?"

The answer:

"Well regulated" doesn't mean "regulated well" any more than a "well
done" steak is always cooked well.

Here's what the University of Chicago's online OED has to say about
well regulated:

well-'regulated, ppl. a.
 - 1709 SHAFTESB. Moralists II. iv. 108 If a liberal Education has
   form'd in us..well-regulated Appetites, and worthy Inclinations.
 - 1714 R. FIDDES Pract.  Disc. II. 250 The practice of all well
    regulated courts of justice in the world.
 - 1812 J. JOYCE Sci. Dial., Astron. xii. II. 126 The equation of
    time..is the adjustment of the difference of time, as shown by a
    well-regulated clock and a true sun-dial.
 - 1848 THACKERAY Van. Fair lviii, A remissness for which I am sure
    every well-regulated person will blame the Major.
 - 1862 MRS. H. WOOD Mrs. Hallib. I. v. 27 It appeared, to her
    well-regulated mind, like a clandestine proceeding.
 - 1894 Pop. Sci. Monthly June 165 The newspaper, a never wanting
    adjunct to every well-regulated American embryo city.

It means roughly "properly functioning" and doesn't imply control by
an outside entity.

The following are taken from the Oxford English Dictionary, and bracket in
time the writing of the 2nd amendment:

1709:  "If a liberal Education has formed in us _well-regulated_ Appetites
and worthy Inclinations."

1714:  "The practice of all _well-regulated_ courts of justice in the
world."

1812:  "The equation of time...is the adjustment of the difference of time
as shown by a _well-regulated_ clock and a true sun dial."

1848:  "A remissness for which I am sure every _well-regulated person will
blame the Mayor."

1862:  "It appeared to her _well-regulated_ mind, like a clandestine
proceeding."

1894:  "The newspaper, a never wanting adjunct to every _well-regulated_
American embryo city."

The phrase "well-regulated" was in common use long before 1789, and
remained so for a century thereafter.  It referred to the property of
something being in proper working order.  Something that was well-regulated
was calibrated correctly, functioning as expected.  Establishing government
oversight of the people's arms was not only _not_ the intent in using the
phrase in the 2nd amendment, it was precisely to render the government
powerless to do so that the founders wrote it.

As to the contemporary meaning and usage of the phrase "well
regulated", see also _The Evolution of a State or Recollections of Old
Texas Days_, by Noah Smithwick (Austin University of Texas Press,
1983), pp. 74-75, as quoted in _Duel of Eagles_, by Jeff Long (Wm
Morrow & Co., Inc., 1990), p. 60:

        "Words are inadequate to describe the appearance 
        of the first Texas Army as it formed in marching 
        order... there a tall'beegum' [hat--JEB] rode 
        familiarly beside a coonskin cap, with the tail 
        hanging down behind, as all well regulated tails 
        should do."

Smithwick was a participant and his description is from 1835.

Also, not so long ago Jerry Stratton wrote in
talk.politics.guns:

"Here's a use I just ran across a few days ago as I was putting
'Sylvie & Bruno' on-line. Note that this is 1889; Dodgson was born in
1832:

...
   'I've no doubt of it," Lady Muriel
   replied. "There's nothing a
   well-regulated child hates so much as
   regularity. I believe a really healthy
   boy would thoroughly enjoy Greek
   Grammar--if only he might stand on his
   head to learn it!' "

Note the juxtaposition of "well-regulated" and "healthy". Somehow I don't
think that Carroll meant that "a legislated out of existence child".