Snowden's trigger was seeing the Director of National Intelligence, James Clapper, lie under oath about mass surveillance to Congress when specifically asked about blind data collection.
When the head of the organisation commits federal crimes without reproach(he was not prosecuted after the details were revealed), who are you supposed to report to except the public?
And Snowden was stealing files months before that happened. Maybe Snowden was on the fence about leaking and Clapper's lie pushed him over the edge. Or maybe it was what convinced him he was right.
But he had already been taking documents by the time Clapper got in front of Congress according to the unclassified house intelligence report on Snowden.
He'd also been denied some lateral movement on teams / projects from what i've heard. I think it's easy to reframe all his actions into hero worship but we have to acknowledge that his original motivations may not have been the end results we see today.
So laws exist, but people don't always adhere to the law for reasons like ignorance and malicious intent. There are also laws which are bad laws & regulation, easily exploitable by clever people, financially lucrative in some cases.
The intelligence services have a difficult task, they need to be on top of their game so they need to know everything and try to prevent problems snowballing unless its not particularly harmful and could be quite educational for future improvement. You have a blank sheet of paper, what would you do to maintain or reduce harm to society?
I say this as someone who has met Andrew Parker, Stella Rimmington and Jonathon Evans and is wise to their ways but not someone who has signed the official secrets but has arguably an "autistic" interest in secrecy and quantifying all walks of life.
Ah man, those poor folks at 3-letter agencies screwing rest of the world and their own citizens. Of course it would be better for them to know everything, have everything, exploit everybody and so on.
That's not how modern democratic society can and should work though
When the head of the organisation commits federal crimes without reproach(he was not prosecuted after the details were revealed), who are you supposed to report to except the public?