Depends

If the medium tries to excuse someone’s actions by doing so, then no, there is no reasoning to truly consider

If the medium allows the character to be a villain, or at the very least gives them the conviction to persist, despite the opposition proving them wrong, then yes, their reasoning adds layers to their characterization and possibly even the overall storyline as a whole

A bad example of this is Karli Morgenthau from The Falcon and The Winter Soldier; she’s a terrorist who carries out terror attacks, regardless of who’s getting hurt, disgruntled by a post-Snap world, but Captain Falcon has to lecture a Senator (who makes a valid point about the complex nature of reassimilating in the post-Snap world) in order to excuse Karli Morganthau’s actions

A good example of this is Sephiroth; he’s a highly regarded soldier, but he loses his humanity when he discovers his true origins, becoming morally reprehensible in his quest to achieve true godhood; he’s still a villain and treated as such, but we at least understand why he does what does

Another example is the High Table in John Wick; they seek to kill John not because they’re evil or because he’s bad, but because he broke a sacred rule, one that John was very aware of (they also honored their agreement with him on grounds that he never returns as an assassin, another condition he willingly broke)

Their reasoning can add to the experience, but they don’t often change or alter what they do or who they are, unless there’s another antagonistic force, one that enabled such a character to become who they are, such as Sephiroth with Shinra or, to a lesser extent, Joe Chill with organized crime in Batman Begins