The two only had a few weeks left of filming, in addition to reshoots, but the friction on set and "creative differences" between the directors and the LucasFilm team became too much to bear, culminating in their exit from the project altogether.
Their ousting reportedly came down to two major factors: disagreements with both LucasFilm head honcho/producer Kathleen Kennedy and writer Lawrence Kasdan.
At the end of the day, the duo's directing style never gelled with Kennedy.
According to Variety, the two were not "granted freedom to run the production in the manner that they were accustomed to" and Kennedy wanted to keep "tight control" during filming. The report adds the "chemistry" between them all was "never right" and Kennedy was not keen on their shooting style or how they interacted with the cast and crew.
Hollywood Reporter also added that when it came down to it, she backed Kasdan over the tone of the film.
Kasdan had his own issues with the directors, which brings us to ...
Kasdan co-wrote the script for the Han Solo film with his son and also wrote the screenplays for "The Empire Strikes Back," "Return of the Jedi" and "The Force Awakens," so it's clear the project is close to his heart.
Lord and Miller, who previously helmed "21 Jump Street" and "The Lego Movie," reportedly preferred an "improvisational style," on set while Kasdan wanted them to stick to the script.
The trio also had a fundamental disagreement over the character of Han Solo himself.
"People need to understand that Han Solo is not a comedic personality. He's sarcastic and selfish," one source told The Hollywood Reporter.
Now that Miller and and Lord are out, Kasdan's name is one of the potential directors being mentioned to replace them to finish the film. Ron Howard is another contender.
LucasFilm insists the film is still scheduled for a May 2018 release. A new director will be announced soon.