Couple years ago I had very bad Harlequin bug infestation on my kale and I asked about it here
https://permies.com/t/259244/control-harlequin-bugs#2471591
At that time I was trying to deal with various type of pests individually: aphids, mites, squash bugs, borers, weevils, beetles, etc. Later I changed to a more holistic point of view of providing plants with nutrient they need so they are healthy and won't attract pests in the first place. It doesn't mean lots of NPK, a lot of time, it is the opposite. This year my garden is largely bug free now, but pollinators are abundant. There are still some around and they are only attracted to sick plants or part of the plant tissues and are not enough to cause damage.
Everyone's situation is unique so I don't think my mineral management is applicable to others, maybe except certain part of the Ozarks and Appalachian Piedmont. In your case, I probably would check soil pH. Over the growing season, organic matter breaks down and soil pH lowers. Brassicas in general like soil to be neutral to slightly alkaline. If you have multiple plants, test on one with lime water. If that's the cause, bugs will leave that plant alone in a few days.