The expansion of doppelgänger lore in The Vampire Diaries caused a lot of controversy regarding Stefan and Elena's relationship. TVD was technically an adaptation of The Vampire Diaries books by L. J. Smith, but the doppelgängers marked one of the first major changes from the book canon (and even what the series had established up to that point). Stefan and Elena were set up as a case of love at first sight, and even when Elena began to fall for Damon, her prior relationship with Stefan was important.

https://screenrant.com/the-vampire-diaries-stefan-elena-doppelganger-controversy-explained/