I think he is very convinced that he is an utterly great guy, that Hertha badly needed him and renounced him to their detriment and that someone of high standing, like him, should expose their evil ways. Even in the short time of his success (basically, October '04 to July '06) i thoght of him as something of a snake oil salesman. I thought it was an excellent idea to step back as national team boss after the success of '06: In a moment when everyone would miss him, when he knew his project would flourish under Löw and when his waknesses as a coach had not become too obvious yet.
He sold off some of his reputation off as U.S. team coach later, but he was still sorta kinda respected when the investor brought him to Hertha as his football brain. That might even have worked out - bringing in talent, networking, brokering deals with large companies, courting the Mayor for a new stadium, etc.. But he can't lead a Bundesliga team through the nitty-gritty of weekly preparation, video analysis and substitution juggling. He couldn't with Bayern, and he could do it even less with a bad to mediocre cadre like Hertha's. It's characteristic that he was able to bring in players with good potential (like Piatek) but then failed to coach them to good performances. Of course, it's everyone else's fault now.
BTW, away to last-place Düsseldorf, kicking off just now. Do or die.