Because a deleted scene from the film shows that Kingpin has been doing business in New York since the Battle of New York. It helped establish he was there when The Avengers was taking place and what happened afterwards, establishing his existence in the MCU proper when Daredevil was cancelled.
It also shows that Matt Murdock appeared earlier in the Marvel Cinematic Universe timeline instead of what everyone assumed. Although in Netflix’s Matt Murdoch appeared in Spider-Man: No Way Home. The deleted scene somehow showed that he appeared earlier.
Daredevil was the first of the Marvel TV shows to get a cancellation notice, though there’s hope that it may return once Disney+ launches. Other than Jessica Jones, which will be continuing in another Netflix-Marvel show, The Defenders haven’t gotten renewed yet either. With no news of movement on that front as well, Daredevil’s small but vocal fanbase is starting to get antsy and will happily take Kingpin in any form they can get him!
After the events of The Avengers, Kingpin continued to terrorize New York City by cheating people of their money and the good guys were always there to stop him. his appearances can now be experienced on a larger scale.
Sometimes writers will bounce ideas off one another when writing a particular story, and other times writers might write a scene for a film and later realize that the scene is better suited for television because it doesn’t fit into the main film’s narrative. That was the case with a deleted scene from the Netflix series Daredevil which has recently been tweeted by one of its writers. It appears to be taking place directly after the events of Avengers Infinity War when Kingpin (Vincent D’Onofrio) is getting outed as one of New York City’s numerous crime boss after the citywide protection racket he ran was lifted with Loki’s death at The Avengers hands.
Ever since the tweet of the scene went viral, it was removed.