All of this is precisely why the episode, which played like a movie, was so crucial to Karen's progression. Daredevil's Season 3 showrunner Erik Oleson explained his reasoning to ComicBook.com. Given how long the quest for answers regarding Karen's past had been, it was totally worth the special installment. So, this fan is grateful he held firm.
For 35 episodes, fans had to wonder about the secret pain she was carrying around. The episode entitled "Karen" was Daredevil's 36th episode. While the big reveal may not have comprised what some fans may have expected, it did fit. Karen is a central character, and Erik Oleson's desire to unravel her past makes perfect sense. As for how Daredevil's writing team arrived at that backstory. Oleson said:
While Karen has toyed with allowing herself love and affection throughout Daredevil and The Punisher's run, she has held back. That makes all the more sense in retrospect. Frank Castle and Matt Murdock are both guys set on denying themselves both of those things too. Thus, making the outlook of her romantic future with either of them problematic, as much as yours truly is wishing for the former to win out.
As of Season 3, we now understand the mechanics of how Karen arrived at where she is. The question is if her journey in Season 3 has opened her heart or mind at all. Part of what makes Karen so redeemable is that she questions whether she is a good person. A tell-tale sign that she is one: bad people tend to seldom wonder.
How much Karen's backstory played into her and Matt's romantic relationship fizzling out is unclear. His behavior in Season 2 indicated he was more interested in Elektra. Hence, a contributing factor in the inevitable frost that set in. As for Karen and Frank, their pasts seem to be playing more of a role.
Warning: Spoilers for Daredevil Season 3 are disclosed below.
In the standalone episode, it was revealed that Karen tragically lost her younger brother in a car accident they were both in. She was driving. The backstory fueling Karen was slightly unexpected as it had nothing to do with revenge. At one point, it seemed like her brother may have been a victim of crime.
As it turns out, it was Karen's messed up life choices that had led to her brother taking desperate action. Add to that not watching the road while driving and it was a formula for tragic disaster. Here is hoping more Daredevil will be in store, so the show can explore its third season reveal more intensely. Or Karen can show up in a heightened capacity on The Punisher's second season to do so.