What is your basis for concluding that he didn’t win? I mean in a greater non-gambling sense he certainly lost at life (unless you consider leaving the casino in a body bag and screwing up the lives of other people including your family and friends “winning”). It’s entirely possible that in the end it will come out that his net-worth was $0 or negative, but he certainly was reported to have a lot of behaviors more in line with an advantage player than your run of the mill gambler.
I was never anywhere near his level of advantage play, but I can tell you that it’s very different from gambling. Gambling is actually kind of fun for those who enjoy it as a hobby (the environment, the emotional pings that come with the occasional win, etc.). As a gambler at the blackjack table you might feel like your decision of whether to hit a hard 16 against a dealer’s King is of importance and agonize over it and as long as you keep your losses at a reasonable level it can be an enjoyable experience.
Being an advantage player is completely different. When you’re doing that the actual gambling part of the activity is rarely enjoyable. In fact, comparing the odds of your different options and weighing how a particular promo might offset a house edge is the only part of the process that would be likely to be interesting about it. When you’re playing blackjack or video poker there is no emotion in the decisions you’re making. In blackjack you’re automatically hitting hard 16 against a dealer’s King without any real conscious thought or feeling. In video poker you’ve memorized where different card fragments rank relative to others for the particular flavor of video poker you’re playing and are simply scanning for the highest ranking fragment to hold. When I would play blackjack online I wasn’t usually paying attention to whether I was winning or losing, but had a mouse in one hand, a mechanical tally counter in the other hand, and was simply burning through hands until I reached N on the tally counter and was no longer required to wager to meet the terms of the promotion. If I was slightly up or down in the end relative to my EV I wasn’t playing additional hands to try to hit any sort of target to cashout. That would be like the clerk at McDonald’s sticking around after punching out to serve a few more customers fries. In fact, a couple years of doing that online killed any enjoyment I’d get out of playing blackjack (or most gambling really) in a real casino for over a decade. Even now I no longer get those same emotional pings from gambling that someone who enjoys it as a hobby might get and I can make myself go through the motions if I’m with friends at a casino, but it’s probably just playing blackjack at whatever the table minimum is until they get sick of playing and walking away +/- $20 from where I started. I’m not complaining here mind you, just noting that the qualities and appeals that might stem from advantage play are very different from those that would stem from gambling as a form of recreation or an addiction.