>A lot of candidates' policies change when they become president. I feel like this is due to a few reasons but a big one may be that they are read into many secret programs (like the NSA one), which give them a new perspective on the "threats". From that the "Not on my watch" mindset kicks in.

The folks in the military and at the NSA have long careers that outlast presidents, more likely they're pretty effective in manipulating politicians than there's some big secret that changes everyones perspective once they're in office.