This is the hardest part of writing for me, especially blog posts.
I can never decide if I'm writing for a) highly technical readers who know 95% of the concepts my idea is based on, and I just want to connect the concepts together in a way the they might not have thought of, b) generally technical readers who have a grasp of the concepts my idea is based on, but will need some details to tie them into the idea I'm building on top, or c) readers who are not-especially-technical in the field, who might be nevertheless be interested in how a few things works, and my idea too.
I feel like part of it is that I am all these readers, depending on the subject. I enjoy reading articles about the areas of software dev I'm deeply interested in, but also about the odd idiosyncrasies of software that is used in fields I don't normally cover, but I also enjoy reading articles about e.g. the challenges involved in developing geothermal drilling systems, or elevator systems in 80+ story buildings, despite having very little experience in either.
I keep going through cycles of "If I just explain this part in a bit more detail, the post will be accessible to an order of magnitude more readers" to "this is way too long, I should cut some explanations, or add footnotes, or more wikipedia links" to "I'm assuming way too much previous knowledge here, or asking the reader to do too much extra work to follow my point".