I actually didn't need to even watch the video to know that chords for heroes were going to show up. In D major this would be I-V-vi-IV and in B minor it would be ... i-VI-III-VII but it's still going to be D major, A major, B minor and G major or B minor, G major, D major, A major. I've referred to this second kind of chord progression as "Gandalf Falls" and it's a sure-fire tear-jerker when you want to musically depict some hero falling in battle. Though that's not the only thing you can do with the chord progression. At the other end of the spectrum, even the minor variation of chords for heroes can be used to express triumph. Care to disagree? Well ... millions on millions of fans of this song by Boston will say you're wrong.
And, hey, Boston made these undeniably trite chords rock harder than anybody else did. There's a distinction to be made between merely trite and what a teacher of mine once called delightfully trite. There's a time when giving the listener the cliche they want is actually the smart and artistically credible thing to do. Know what? Boston figured that out and they delivered in spades. But you know what else? Even the guys in Boston knew you had to rotate the chords around if you wanted to have more than (one) a feeling. But this isn't the place to explain that neapoliton substitutions are part of what saves that other golden oldie from Boston from being completely trite. Chromatic mediant substutions account for that ... but we're not going to assume that people trying to write a worship song in five minutes or less are good enough guitarists or competent enough at music theory to not what chromatic mediants or chord substitution are.