IT'S LUKE. HE'S FORESHADOWING LUKE BLOWING THE THE DORK STORE. IT'S NOT ABOUT WHATEVER STUPID COMIC BOOK SHIT. THE FORCE WAS SUBTLE IN THE OT. IT DIDN'T MAKE YOU A SUPER HERO. IT WAS WEIRD ESOTERIC WIZARD SHIT THAT NO ONE TOOK SERIOUSLY. YOU FOOLS. YOU HORRIBLY ILLITERATE FOOLS. YOU HAVE MISSED THE POINT. THE POINT HAS EVADED YOU. IN YOUR QUEST FOR EMPTY SPECTACLE AND CGI VOMIT YOU HAVE LOST THE CORE POINT AND PURPOSE OF THE ENTIRE STORY. THE PIVOTAL MOMENT ISN'T SOME EDGELORD DIPSHIT IN A KORN T-SHIRT BLOWING UP A PLANET. IT'S WHEN LUKE COMMUNES WITH THE FORCE TO LAND AN IMPOSSIBLE SHOT TO ALLOW A SMALL FORCE OF TACTICAL FIGHTERS TO DESTROY AN OTHERWISE INVINCIBLE FASCIST DEATH BATTLESHIP! YOU FOOLS! WISDOM HAS ABANDONED YOU! SOPHIA WEEPS AT YOUR APPROACH! ALL HOPE IS LOST! HUMANITY IS DOOMED! IGNORANCE AND SHITTY SEQUELS ARE THE ETERNAL DOOM OF HUMANITY!

Also; "Why was Vader behaving in ways that are inconsistent with his portrayal in media decades later?"

BECAUSE IT WAS A STAND ALONE MOVIE YOU LITTLE SHITS! THEY DIDN'T THINK IT WOULD BE SUCCESSFUL ENOUGH TO HAVE A SEQUEL! FICTION ISN'T REAL! IT'S NOT INTERNALLY CONSISTENT ACROSS EPISODES BECAUSE IT'S WRITTEN BY PEOPLE TELLING A STORY! IT'S NOT REAL! IT'S FUCKING FICTION!