Unfortunately there isn't a specific answer to the question of racecraft besides "race more". While the best drivers in the world may have some amount of talent built in, racecraft is a learned skill that nobody is born with. And there's a lot going on - you have to visualize your line, understand the machine, plan your inputs, expect the outcomes, keep an eye on traffic, think ahead about what they will do, visualize where other cars will be in the future, etc.
The only way to learn all these things and put these skills together is to keep racing and practicing. You seem like you're interesting in getting better and you've already made several observations so keep making more observations. Pay attention to what happens in certain situations, pay attention to the decisions other drivers make, etc. Eventually you'll get to the point where you just have a feeling that a divebomb is coming before you even get to the corner, can plan on it, watch the asshole go flying past you because they outbraked themselves, and continue on your way with a smile on your face.
I'd recommend watching videos by
Super GT especially, and
Basic Ollie who are my two go-to channels for GT. There are a few other "famous" GT streamers with informative videos as well. Super GT's humor just suits me well and his racecraft is extremely good. If you watch and learn from the best and try to emulate that, you'll get better over time. Just remember that the way GT's points systems work means it's going to take a lot of repetition to raise your ratings incrementally. Pro tip: If you're struggling to perform in Daily Race A, you may simply have to be more aggressive. Safety Rating is easy to gain back in the future so if you do a little bump and grind here and there, no big deal. Most higher-rated drivers avoid Daily Race A because it's kind of a meat grinder where annoying things are expected to happen.