Over the years, the Marvel Cinematic Universe has slowly filled in the gaps of its timeline with its films and TV shows. However, one of the most overlooked decades has been the '90s. Aside from brief scenes in Black Panther, Black Widow, Ant-Man and Captain Marvel, the state of the world was still largely unknown. However, this was possibly done on purpose, as espionage became the sole method to combat enemies.
One of the biggest threats during this time was the Black Widow program. Training young girls to be remorseless killers was no easy feat, but Draykov cracked the way to do it and planned to use them to infiltrate the world and take over. While many likely had no idea how to combat this, there's a strong chance that SHIELD was very aware of this threat. In fact, they even had their own deterrent in the form of Agent 19, aka Mockingbird, aka Laura Barton.
Black Widows Slowly Took Over In the '90s
The '90s was a turning point in world history as the technological age was finally gaining steam. As a result, spy work also had to advance. As the early '90s had shown in Black Widow, this was a slow process. So slow, in fact, Russia still had to send sleeper families to build up a facade and use it to steal secrets before SHIELD had any idea what had happened, like what Red Guardian did in 1991, and this was happening worldwide as more and more agents of Draykov began to execute their plans. At that point, there was likely no equal measure to face these threats, so it forced SHIELD to fight fire with fire.
To make matters worse, Draykov had never stopped training Widows, so even though some were defeated or apprehended, there were more coming out of the Red Room every day. It became as dangerous as Hydra in that regard, as there was no logical way to stop them. However, by fighting fire with fire, the key was to train an agent that could face the dangers head-on without risk of overexposing themselves or their personal lives. That's where Laura (or Bobbi Morse) came in.
Mockingbird Was Likely SHIELD's Best Defense Against Black Widows
SHIELD may not have known which people were already Widows, but by training Agent 19, they could have someone equally skilled infiltrate their ranks, acting as an ally or Widow herself. This would explain Laura's connections that she's gained and utilized in Hawkeye. In fact, her time as an anti-Black Widow was possibly how she met Clint Barton and even Natasha Romanoff.
Being that she was so well traveled and possibly an ally to Romanoff as a false Widow, she and Hawkeye were likely the ones who convinced her to change her ways. Eventually, Laura knew her time as the best defense against Widows had to be over, and she retired. Since then, she's still been a great help to her friends and loved ones when needed, but there's no doubt that if the need arose, she could fall back into her training at a moment's notice.