Evil Vulcans became the enemy in Star Trek: Enterprise, just as corrupt Klingons were often the enemies in Star Trek: The Next Generation. The Vulcans and Klingons both made their debut on Star Trek: The Original Series, which established many elements about their species. However, with the episodic nature of 1960s television, TOS did not spend much time developing complex cultural histories for the alien species it introduced. TOS would reveal hints about the Vulcans when it pertained to a specific storyline involving Spock (Leonard Nimoy), and the Klingons served as general enemies for Captain James T. Kirk (William Shatner) to oppose.

https://screenrant.com/star-trek-enterprise-evil-vulcans-tng-klingons-similar-explainer/