The Avengers' director Joss Whedon's decision to make Agents of SHIELD explains why its connection to the Marvel Cinematic Universe was doomed from the beginning. Long before the debut of Disney+, which now exclusively houses Marvel Studios small screen projects, the Marvel TV branch existed. The idea was that shows like Agents of SHIELD and Agent Carter, both airing on ABC, expanded the storytelling that the franchise was doing on the big screen. However, while the series routinely referred to the events of their movie counterparts, the blockbusters barely acknowledged their existence.

https://screenrant.com/the-avengers-agents-shield-mcu-show-crossover-joss-whedon/