There is nothing cultish about it. This isnt the first time a director's cut has been released. Ridley Scott has released what 5 Blade Runner Director's cuts?
The only difference in this case is that it wasnt just the studio messing with the director's vision, they literally fired the guy and had another guy come in and completely butcher his movie. Dozens of shots in the trailers were not in the final version. Entire scenes were taken out. Embarrassing scenes with Flash grabbing Wonder Woman's tits were added in. Entire Junkie XL score was thrown out. The entire look of the final battle was changed. This was far far worse than what they did to David Fincher's alien movie.
Is it really that weird to think that people would want to see the original version?
Also, unlike say David Ayer who also had his movie butchered by a trailerhouse company no less, Snyder has a far larger following due to his work on 300 and Watchmen. Man of Steel is widely derided on the internet as an awful movie, but I thought it looked stunning and had some great fight sequences.
His fans just want to see more of this.