First, for those that aren’t already aware YouTube Demonetization seems to be spearheaded by crappy Artificial Intelligence Bots. The process starts immediately when your video is being processed. The content of your video, title, thumbnail, description and tags all play a part as well as your YouTube Channel Authority. Videos can also be demonetized long after being posted through some process I don’t understand.
YouTube checks your video for sensitive content and rates it according. It’s important to note these ratings aren’t just about money in the YouTube Partner Program. These ratings have a huge impact on censorship for your videos. A video ok for all advertisers is the same as a video ok for wide distribution.
A year ago this rating system was discovered in the YouTube webpage code under the HTML line “excluded_ads”.
Numbers on the excluded_ads line were deduced to correlate with the following:
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102=“Profanity and rough language” (very wide)
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104=“Sexually suggestive content”
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105=“Tragedy and conflict” (War, army, headshot etc)
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109=“Sensational and shocking”
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113="Violence?"
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115=“Sensitive social issues”
Unfortunately the “excluded_ads” line was removed so I can’t analyze the problems holding back my videos. 
Meanwhile, here are some useful tips to avoid trouble:
Also, here is a link to an old YouTube Evaluator Guide:
What is YouTube’s New excluded_ads Line?
There are many skilled techies here on the Level 1 Forum. My big question is what did YouTube change the excluded_ads line to in the page source code? My HTML skills are pretty crude, but I bet the info is still there in some form.