Pardoning Chelsea Manning is a slap in the face to anyone who ever served in our military, me included. Absolutely erases any goodwill I ever felt towards Obama.
As for Bergdahl, he abandoned his post on foreign soil and put soldiers at risk during wartime. I've read that people died looking for him. Mistakes have consequences and his certainly did.
I would think that it shouldn't be more so than George W. Bush (and several members of his administration) and Trump being elected President. Both of these presidents garnered a large majority of the military vote, while either avoiding service or being unaccounted for and never serving in Vietnam despite their age/eligibility. Bush's team threw an active CIA agent under the bus to cover their asses. Morality related to the safety of people in the field was a none issue for Dubya's administration. Trump has the further audacity to call out military leaders and by proxy the work that soldiers are doing on the ground, putting their lives at risk for our nation (and various other agendas). He has neither the understanding of military strategy/actions nor the concern of service men and women (and certainly not their families), insulting fallen soldiers and their families by questioning their loyalties based on their religion. He, like way too many American citizens, is too fucking dense to realize that the First Amendment is the foundation of all of our freedoms and therefore our nation...except when it comes to spewing hateful, fear-mongering, misogynistic, un/misinformed, prejudicial, unfounded, and reactionary statements.
Flagrant lack of respect for the sacrifices made by our military, whether you agree with their actions or not, should be a potential disqualifier for anyone that aspires to be Commander in Chief. Or even those that end up in the position nearly by accident.
That said, I'm not sure how one gets let off for committing treason. The traditional punishment was death/execution, and maybe that is a bit harsh unless true strategic compromise and deaths can be attributed to a given treasonous act. I'm sure fear of death is at the heart of why Snowden isn't rushing back to the U.S. Manning is a very unique case given the entirety of her circumstances. By all accounts transitioning is extremely difficult for anyone, add to that being in the military which has traditionally frowned on homosexuality (and their myopic perspective won't distinguish between these two different things). So there are larger psychological issues that the military isn't prepared to understand, let alone deal with. A significant amount of her transition has happened while in various military prisons while being tried for espionage...I can't even begin to imagine what that might be like.
And even add to that her age at the time and to whole concept of evaluating one's life...if you are among that reassess what the military does while you're there. It can easily be argued that one might think they're doing something for a greater good or purpose. The files leaked weren't plans for further attacks or impending actions, but information that would one day be available via the freedom of information act. Again, that doesn't make it right, but it is not the same as leaking secrets that would compromise active soldiers.
She'll never be a position to access, let alone disseminate information like this again. Being in prison for discovering a new set of ideals based on disillusionment seems harsh, but there are laws about this in place and they are there for a reason. According to President Obama's people, Chelsea has serve close to the average amount of time as others that have been imprisoned for the same crime. If that's true, it becomes another consideration...but I'm not having any luck finding data relating to time served for this/similar crimes.
Any deaths related to searches for Bergdahl are questionable. The searches were officially ended and the six soldiers that were part of battalion that died, died on other missions. The accusations that he was responsible for their deaths come from the idea that they never stopped looking for him, which is purely speculation. We can't know how quickly after he left his post he was captured or if he would have come back. Letting assumptions fueled by anger be the basis of judgment and not actual information is why we are inaugurating a piece of shit for POTUS in two days. Essentially, it is ALWAYS a bad idea.