If my post looks good, then I move it off the airgapped machine to my main device where I upload it to my Ghost instance and then seen by thousands, or even millions if it gets picked up by other bloggers/news outlets who would amplify your message and spread it far and wide.
Providing you have monetized it, you can generate revenue, although to really earn properly from it you would need a small staff of writers and master Commission Junction / Amazon Associates and you would need to consistently churn out well written high quality posts and also build your audience organically over time.
And which topic should I write about. How should I decide this?
The site is huge and they're doing affiliate marketing on multiple pages, not just my example link.
Also: The articles are also authoritative, authentic and not mere blogspam. They explain everything in detail and offer insights; the affiliate links are not the sole purpose: they want to write a blogpost too!
Medium can suck though, as their algorithm decides whether your posts will be shown on the homepage. Personal self hosted blogs on the other hand can be hard to optimise for search engines, which is something medium is great at.
Don't try to make blogging your main thing. You will either fail or it will take along time for you to see any decent sums in the first place. Do it on the side, and if it takes off then you can consider doing it full time.
What brings about this desire and direction for a career change?
Still trying to figure this one out and I think I'm getting closer. If I remind myself that I really like talking about this subject and that I want to share what I know with as many people as possible, so that they might grow on my shoulders, than I can find some energy.
"The hardest part is starting." ~ someone notable
If you aren't excited to do that thing every day, why are you doing it?
And if you want to make money, I suggest you try e-commerce.