The thing I’ll say about it is that he’s a character that, like Darth Vader, worked on a primal level for people. He touches on something fundamental in our psyche, and in those three movies, he, to me, was the most powerful bit of psychological imagery. I think that’s why fans were drawn to him and why the canon was eager to tell more stories about him. In a galaxy populated with very dangerous people, he’s always been in the top group of dangerous people. So the opportunity to put him in the movie and give him the element of these mechanical legs, which rhyme with Luke’s mechanical hand — it seemed like it could work.
Source : http://www.latimes.com/entertainment/movies/la-et-mn-solo-star-wars-kasdans-maul-jabba-20180526-htmlstory.html