Moore has explicitly made his brand separate from the GOP brand. I don't think it will make much of a difference, particularly now that sex scandals are raining down on both sides and the allegations against Moore remain unproven. It could hurt Bannon potentially if the allegations turn out to be true, but he can correctly say that he supported Mo Brooks in the first place and that American law presumes innocent until proven guilty.
If he wins and then gets expelled from the Senate (my preferred option), it could help democrats by exacerbating the republican civil war, but it would probably mean senator Brooks, which is way better than senator Moore.
Bannon never supported Brooks, he always supported Moore.
Try actually reading the article wikipedia (your source on this) cites and you will find that it is from August 28th. The primary with all of them was August 16th. Bannon only endorsed Moore after it was down to a runoff between him and Strange. The coverage of Brooks had been very favorable on Breitbart until he lost and it switched focus to promoting Moore and ensuring Strange would lose the runoff.