What was the logic behind the Richie Sexson trade?

I want to revisit what was clearly the most disastrous trade in the history of the Diamondbacks franchise, because I'm hoping someone around here will be able to explain to me the logic behind it. I wasn't actively following the D-Backs in 2003-2004, so I didn't get to hear the argument for the trade at the time. Looking back at it today, it looks absolutely inexplicable.

In December 2003, the Diamondbacks traded Junior Spivey, Craig Counsell, Lyle Overbay, Chad Moeller, Chris Capuano, and Jorge De La Rosa to the Milwaukee Brewers for Richie Sexson, Shane Nance, and a PTBN who turned out to be Noochie Varner. Sexson proceeded to get injured and miss virtually the entire season, playing only three games before departing Arizona as a free agent. So the trade was disastrous because Sexson got injured. But wasn't it also disastrous even if he had panned out?

First, let's look at what we got in the trade:

- Richie Sexson: one of the all-time great baseball players, Sexson had belted 45 home runs in 2003 for Milwaukee and put up a slash line of .272/.379/.548.  Clearly a piece worth acquiring.  On the other hand, he was due to become a free agent at the end of 2004, so we were paying for only a year of team control.

- Shane Nance: a 26-year-old relief pitcher with a 4.81 ERA in 2003 (and an even worse 5.84 ERA for us the next year).  Not worth even a single player we sent to the Brewers. According to Wikipedia, "He is now an outstanding Outside Salesman for Flow-Zone LLC."

- Noochie Varner: a career Minor Leaguer who only reached AAA once in his career.  No longer plays baseball, but according to this story, "He just might still be active in the online poker circuit."

The upshot: we got Richie Sexson, and really only Richie Sexson.  And only for one year.

For this, we gave up six real, live players.  Five of them were Major Leaguers, with four being everyday players.  Here's a closer look:

- Junior Spivey: our starting second baseman, Spivey put up a slash line of.255/.326/.433 for the D-backs in 2003.  The previous year, he'd batted .301 and made the All-Star Game (admittedly thanks to D-backs and ASG manager Bob Brenly).  Though he later flamed out of the majors, Spivey was viewed at the time as a good player and a solid contributor.

- Craig Counsell: A solid veteran, two-time World Series champ, key clubhouse presence, popular with fans, and the definition of a clutch hitter.  Counsell was coming off an injury-plagued 2003 season, but in his last healthy season before the trade (2002) he had posted a slash line of .282/.348/.351.  Our everyday third baseman when he was healthy.

- Lyle Overbay: A 27-year-old first baseman with power potential  The D-backs weren't particularly hot on Overbay and had relegated him to the minors for parts of 2003 (particularly after we acquired Shea Hillenbrand), but he'd still managed to put up stats of .276/.365/.402.  Definite trade bait, at the very least.

So as you can see, the FO decided to trade our entire infield for one year of Richie Sexson.  Well, all right, a player like Sexson doesn't come cheap.  But when you realize we're only halfway through the players we gave up...

- Chad Moeller: previously our backup catcher, Moeller platooned with Robby Hammock at the position in 2003.  He put up a respectable .268/.335/.435, though Hammock was somewhat better at.282/.343/.477.

- Chris Capuano: of all the players we gave up, I find this one the most inexplicable.  Called up from Triple-A near the end of the season, the 24-year-old Capuano had gone 2-4 with a 4.64 ERA as a starting pitcher.  The numbers weren't great, but it was Capuano's first year back from Tommy John surgery, and the stuff was clearly promising; Capuano has remained a back-of-the-rotation starter ever since, and was an All-Star in 2006.  Given Elmer Dessens' bloated 5.07 ERA in the starting rotation, and the injuries to Randy Johnson and Curt Schilling, one would think the D-backs would have wanted to develop a guy like Capuano.

- Jorge De La Rosa: you can't really blame the FO for not realizing De La Rosa had frontline starter potential given that we had just acquired him a couple of weeks earlier.  Still, he was dealing in Boston's farm system, putting up a 2.98 record across AA-AAA and giving up less than a hit per inning during that span.  Clearly a shutdown reliever type at the very least.

Looking at this list, here's my question: why would anyone make this trade, ever, under any circumstances?  Richie Sexson was a great player.  We were getting only one year of Richie Sexson.  Was one year of Richie Sexson worth our entire infield, including two guys (Spivey and Overbay) who had years of team control left?  Was one year of Richie Sexson worth that plus our starting catcher, a promising starting pitcher (also under long-term team control), and a shutdown reliever who was way better than the one we were getting from Milwaukee?  Is any player, ever, worth selling the heart and soul of your team for a single year of control?  What possible argument could be made for this trade, even assuming Sexson had a career year?

I don't know much about stats or about the team during these years.  I do know that the trade was disastrous for us, but I want to know how anybody could ever have seen it as potentially non-disastrous.  How was this ever a good idea?