You sound like you don’t understand how Electors are chosen.
Each party has a slate of Electors in each state. They select the slate based upon party loyalty.
If their slate wins, they get to represent their state in the Electoral College. Sure Don Trump Jr could be free to vote for Hillary...but it’s not going to actually happen.
In general, the handful of “defectors” have only been to make a statement when the election is not in doubt. They don’t switch to the opposing major candidate, but they do things like reversing the votes for President and Vice President (for the already losing candidate).
I know how the Electoral College works. And I agree thus far it has been effective.
My points are that as we grow more radicalized, we may enter a place where so much “faithlessness” occurs it damages the integrity of the elections.