I discovered there are certain keywords that if used in a video's title, description or tags, can automatically trigger Youtube's AI demonetization bot. If left unedited prior to appeal, it could cause the video to not pass manual review:
damage
disaster
injuries
accident
crash
collision
severe
destroy
fatal
tragedy
flooded
There are probably more of these trigger words, but all of my demonetized videos had one of these words in the description. Even if nothing graphic is shown on the video, if the description has something like "this tornado outbreak destroyed five houses and injured ten people", it could trigger the AI bot and make the video ineligible for ads, even if it is reviewed manually.
Basically you have to make the video description/title as "snowflake-friendly" as possible, as if you're describing the event to a young child. I have had two videos successfully appealed just by removing the word "accident" from the description.