We have no idea about Wenger's personal life or his motivations.
He and his family are reportedly very settled in London, with his daughter in secondary school having spent her whole life in the capital.

I have the book, and I honestly don't remember that quote (although it was a few years ago that I read it, so feel free to direct me to it).
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It was a while ago that I read it as well, and I have since tried (unsuccessfully) to find and quote it verbatim - but for some reason it was just a quote that always stuck out in my mind. If I only I could find the bloody page.

But either way, that doesn't seem to explain all the failed transfers over the years. We've been in negotiations with a number of potentially top players over the years (Alonso and Mata are the most notable examples) only for the club to fail to push them through. That doesn't signal an unwillingness on Wenger's part, but a problem in terms of negotiation.
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I know you're making a general point and those are two specific examples, but I think those instances of failed transfers are normally under mitigating circumstances. Alonso, for example, was never that likely a deal in the first place, as Liverpool were still fairly reputable (and if I'm not mistaken, finished above us that season). Also if you factor in the fact that we had Fabregas, Nasri, a still fairly popular Denilson and had just signed Ramsey, it may have just been a cheeky inquiry to see if the deal was value for money. And the blame for the Mata debacle is still hotly disputed - a work colleague of mine lives next to Colin Lewin, and he claimed at the time that the deal collapsed because of Wenger dithering - on the other hand, there are sources claiming that Gazidis fecked up with the release clause deadline.

When there's been a target that Wenger has really wanted, we've rarely had that much trouble. Gervinho, Koscielny, Podolski, Giroud... those are a few examples. I've found that the most troublesome transfers always seem to be the most anticipated (as with Mata and Hazard, for example, where every supporter was sporting a chubby at the prospect).

"Alonso, for example, was never that likely a deal in the first place, as Liverpool were still fairly reputable (and if I'm not mistaken, finished above us that season). Also if you factor in the fact that we had Fabregas, Nasri, a still fairly popular Denilson and had just signed Ramsey, it may have just been a cheeky inquiry to see if the deal was value for money."

We finished above Liverpool the season before/the Summer we tried to sign Alonso, but more importantly, Liverpool were trying to sell Alonso to raise funds to sign Gareth Barry. We had been attempting to sign him (and Gokhan Inler as a back-up...another deal which failed) pretty much the entirety of the transfer window, right up until the day it shut (a deadline day bid was issued in addition to the previous bids). The fact that Liverpool were looking to sell suggests this was definitely a feasible transfer, and the fact that we made attempts to sign him (and other DMs) implied Wenger was genuinely looking to sign a new defensive midfielder.

On the Mata front, of course, we'll never really get full disclosure as to why the transfer didn't materialise, but it makes no sense for Wenger to have dithered on the issue. Wenger and his scouting network are incredibly meticulous (Bakary Sagna was watched over 40 times before the decision was made to sign him, for example) so I find it hard to believe the club would get so far into negotiations without Wenger and his team being sure he was a suitable target. We then later signed Arteta and Benayoun, which compounds the suggestion that Wenger had been looking to add creativity to his ranks, making the claims that Wenger was the reason the Mata deal never came to fruition even less logical.

"When there's been a target that Wenger has really wanted, we've rarely had that much trouble. Gervinho, Koscielny, Podolski, Giroud... those are a few examples. I've found that the most troublesome transfers always seem to be the most anticipated (as with Mata and Hazard, for example, where every supporter was sporting a chubby at the prospect)."

I don't think you can really infer from successful transfers that Wenger signs the players he really wants; you could just as easily point to a whole host of failed transfers and argue the opposite.
It's worth noting that none of the players you mention were very high-profile, and all of them came for, at most, just over £10m.
It is on the more costly transfers (the sort that Wenger is harangued for completing) that we always seem to struggle; we failed to sign Alonso, Mata, and would have failed to have signed our record signing, Arshavin, were it not for a snowstorm preventing him from leaving the area on deadline day.

Δ or rumoured interjection of Usmanov to the Zenith board to forgive Arshavin's loyalty bonus.

Interesting! To be honest, it wouldn't surprise me!