“I don’t just miss the role,” he continued, “I miss [Mariska], so any opportunity to get back into a room with her is valuable to me. Part of the reason I became Barba, and that it turned into the show that it did for me, was the way I hit it off with her and that was surprising. What was supposed to be a guest starring spot that [former showrunner, who’s back for Season 21] Warren [Leight] had written for me morphed into something very rich and surprising … entirely because of the space that was created between me and Mariska.”
“It’s chemistry — it happens or doesn’t, and it happened,” he said.
We’d love to see their chemistry return to our screens once again. New episodes of Law and Order: Special Victims Unit air Thursdays at 10 p.m. on NBC.
Source : https://www.distractify.com/p/why-did-barba-leave-svu