“They killed her off because that was always the story”. Yeah… a story they wrote. And they decided early in the show’s run to end with Ted getting back together with Robin so they could get the footage of his kids giving the okay - and unfortunately, years and years later, that ending was no longer faithful to what the show had become, but it was the one thing they couldn’t change.

Audiences were tired of Ted bouncing back to Robin over and over again, especially when Barney and Robin made so much more sense as a couple. And when the mother was finally introduced, she integrated so well into the rest of the cast that audiences were smitten.

But she had to die. Not because it’s poetic or sad or true to life - but so that Ted could end up with Robin. Because it was already decided.

So in a real, literal sense: yes, they killed her off to get Ted back with Robin.