The Flashpoint storyline in the comics was actually written by DC Entertainment President and CCO Geoff Johns, who oversees the DCEU for Warner Bros. The story has Barry Allen travel back in time to try and stop the murder of his mother.
The Flash movie has been through the ringer over the last year, getting several different directors and a page-one rewrite.
Flashpoint was done in a fashion during The Flash season 3 on The CW, but many fans feel it didn’t quite live up to the name.
Not to mention that it makes The Flash movie much more appealing, since it will be a big event.