Sometimes the official charges are determined more by what's easiest to prove in court rather than what everyone knows is the most egregious of the crimes.

Court procedures aren't about public opinion, and it's easier to prove someone shared government secrets than it is to prove they did stuff that's so heinous that they obviously hid most of the real evidence. Like it or not, a couple of creepy emails ridden with thinly-veiled euphemisms isn't enough for the courts.

Edit: I'm not suggesting the British government particularly cares about the egregious crimes, just that this is sometimes why it seems like someone is charged for reasons that aren't quite the right ones...