Nationally, Cohen had the bad luck to come into the game before Michelle was done. Internationally, her two Worlds silver medals were second to all-time best performances of Arakawa and Slutskaya.
That's sports. IMHO it doesn't require psychoanalysis.
Cohen's failure to win big events should not just be put down to quality of competition:
2002 Olympics- fell in long, Hughes who was trailing her after the short wins gold.
2002 Worlds- fell in short, fell twice in final long.
2003 U.S Nationals- stumbled in short, fell and stumbled twice in long.
2003 Worlds- fell in short, fell twice in long.
2004 U.S Nationals- led after clean short, fell and stumbled in long.
2004 Worlds- again led after clean short, botched jump and had other shaky landings in long, still losing only on split decision.
2005 U.S Nationals- bobbled a jump in short, fell on one and bobbled another jump in long.
2005 Worlds- had small stumbles in every program.
2006 Olympics- fell twice in long.
2006 Worlds- made a total mess of both her qualifying and long performances.
Clean competitions by Sasha in World, Olympics, U.S National Championships: Zero.
Winners of all World events since 1999, and of all U.S events since 2002:
1999 Worlds winner- Maria Butyrskaya clean
2000 Worlds winner- Michelle Kwan clean
2001 Worlds winner- Michelle Kwan clean
2002 Olympics winner- Sarah Hughes clean
2002 Worlds winner- Irina Slutskaya clean
2003 Worlds winner- Michelle Kwan clean
2004 Worlds winner-Shizuka Arakawa clean
2005 Worlds winner- Irina Slutskaya clean long
2006 Olympics winner- Shizuka Arakawa clean
2006 Worlds winner- Kimmie Meissner clean
2007 Worlds winner- Miki Ando clean
2002 U.S Nationals winner- Michelle Kwan clean
2003 U.S Nationals winner- Michelle Kwan clean
2004 U.S Nationals winner- Michelle Kwan clean
2005 U.S Nationals winner- Michelle Kwan clean
2006 U.S Nationals winner- Kwan absent, Cohen not clean
2007 U.S Nationals winner- Kwan absent, Meissner not clean
As you can see every World event winner since 1999 went completely clean, except for Irina in the 2005 Worlds short program, but she came back with a completely clean long. Every U.S Nationals that Kwan was in since 2002 was won by a clean short and clean long program. As you can also see Sasha NEVER did clean competitions, in fact never did a clean long program, in any of those events. Pretty hard to win big events in an era were everyone who wins them did so with a clean competition, when you fail every single time to put together a clean competition, or even a clean long program ever.