There are many players with "high tech skill" that don't place well in tournament. And same goes for the opposite some players have less tech skill but place well. Melee is much more about neutral, knowing the matchup, adapting, etc. If you look at HBox arguably the best player he plays one of the least tech heavy characters. Syrox, Reino, Absent page, westballz all have incredible tech skill but dont win tourneys.
Although I agree with your general sentiment, merely reducing the skills of Syrox, Absent Page, and Westballz to "spamming techskill LOL" is extremely dangerous and unproductive for discussing what makes Leffen better than Syrox/other high-level foxes. Syrox, Absent Page, and Westballz are all still better than 99.99% of all players and they generally have excellent resumes (although Westballz can be quite upset-prone). In fact, Absent Page just won Dreamhack Atlanta, beating S2J, ChuDat, and many other high-tier players on his way.
IMO, what makes Leffen better than other high-level foxes can boil down to consistency and composure during stressful situations. Leffen is a techskill monster that can easily be argued to be on the same level as Syrox in terms of techskill, but Leffen also is much more consistency with very important techskills, such as ledgedashes, cancelling shines, and pivots. Ledgedashes are significant for getting back on stage and during edgeguard reversal situations, and pivots are important for many kill setups from throws. He also generally tends to be an efficiency monster, going for more guaranteed followups and better coverage options than more specific and volatile setups that require much more precise scenarios and cover less of the opponent's defensive options. This is especially important to keep in mind during edgeguarding situations. He also does much better during high-pressure situations, where Leffen and his opponent players may both be down to their last stock and in high percents, or when Leffen is down multiple stocks against an opponent and needs to make a big comeback. Leffen trusts his skills as a player, and has learned to panic less over the years. This strong mentality has mostly come from experience.
These traits really aren't unique to Leffen, however, and all of the gods all possess these traits (yes, including Hungrybox), which is why they are gods and can stay consistent every year.
