"Knowledge is power... power is power..."
In Game of Thrones, power is everything. It's why alleigances are forged, wars are waged, kingdoms are divided, and Peter 'Littlefinger' Baelish has a reason for being.
Indeed, Littlefinger is a great example of the power structure within Westeros: anyone can climb to the top of the ladder, even if you're from a nothing house in the Fingers.
Just as quickly, however, you can find it all going up in the flames of wildfire - you only need ask the hugely powerful players who were wiped off the board in Season 6: Roose and Ramsay Bolton, Walder Frey, Margaery Tyrell, and the High Sparrow.
Heading into Season 7 the balance of power has been completely shaken. The North has changed hands, Daenerys has departed for Westeros, and Cersei's claimed the Iron Throne despite having seemingly little right to do so (laws of succession don't matter when you have, ah yes, power to take it anyway). We're heading towards the endgame, which means things are really shaking up.
In the fitting (and true) words of Varys: "“Power resides where men believe it resides. No more and no less...
"Ofttimes a very small man can cast a very large shadow.” And so too can all of these.