The Obama Administration didn't only not prosecute Bush Administration war crimes, they squashed Spain's attempt to prosecute them and represented Rumsfeld in court against torture charges. The Obama Administration left the door wide open for us to be lied into war again.
"Look forward, not backward" doesn't apply to the rest of us. Ask Chelsea Manning. Does it mean that we should only arrest people if we can catch them before they commit a crime? Obama saying that nobody should be above the law in his "look forward" statement was at best complete and blatantly obvious hypocrisy. I believe it was an outright lie and he really does believe presidents are above the law. Why did Obama doom us to be lied into war again?
There are some more obvious possible explanations. I for one was surprised at the veracity of anti Obama derangement syndrome. Right away, conservatives cheered that we didn't get the Olympics. They or their kids might be stuck in low paying jobs, or not have jobs at all, but they still vote for politicians who block jobs bills. Imagine what the backlash would have been if Obama had prosecuted Bush Administration officials? Even if you can't imagine division being any worse than it is, it is understandable that Obama wouldn't try to make it worse. Presidents try to unite the country, especially soon after elections, which is when he made his "look forward" statement.
Fear of the power of the elite and the military industrial complex is another possibility. And Obama might not want to set a precedent that could someday end up being used against him. But I want to speculate on a more theoretical rational. Those in charge believe starting wars is in the realm of presidential responsibilities.They consider it to be part of the job description. At worst they see the war crimes as a bad decisions, but they were the types of decisions that Bush was responsible for making. Wars can gain territory or resources. Some people think that's justified. Maybe a war only keeps us armed for the next war that we really do need to fight. The Gulf of Tonkin false flag and Vietnam War escalation that followed it might have slowed the spread of communism. The domino theory was the conventional wisdom at the time. Maybe it would have come true if less had been done to fight the spread of communism.
But the best example I can think of is Pearl Harbor. Overwhelmingly, Americans didn't want to get in to WWII before Pearl Harbor was attacked. If we hadn't, we'd be speaking German now. Some people believe Roosevelt knew Japan would attack Pearl Harbor. I personally lean toward a belief that there was too much false information mixed in with the intelligence for him to know. But I'm nowhere near positive about that. If Roosevelt did let Japan attack, and maybe even egg them on, it was the historically correct decision. It got us into the war while there were still allies in the fight. If we hadn't helped gang up on the axis countries there wouldn't have been anybody else left when they came for us. Roosevelt might not have know it at the time, but Germany very likely would have developed the atomic bomb instead of us. A lot more people would have died and we would have been taken over by the Nazis. Roosevelt sacrificed a relatively few people to save the whole country. Roosevelt didn't know it would turn out to be the right decision. Just like Bush didn't know attacking Iraq (against international law) would turn out to be the wrong decision. At least I think that might be how people like Obama rationalize not prosecuting war crimes. Too them, it wasn't criminal. It was a bad decision.