The Flash, directed by Andy Muschetti, was a box office flop, despite much anticipation. But the movie was originally meant to be very different. The Flash would have been crucial to the development of the DCEU, as one of his most important villains, Eobard Thawne, was meant to be the one pulling the strings across all the films.
Source:https://www.cbr.com/reverse-flash-zoom-villain-almost-big-bad-dceu/