As a technical writer if push comes to shove I would recommend leading off with what you need to do first and foremost, and then going into detail about why as needed. You should optimize your content for the audience that is already convinced and just wants to know what they need to do in order to stay safe. You can follow up with the information explaining why they need to do this for the secondary audience of people who still need convincing.
In other words, if you think about it in terms of the typical inverted pyramid model of journalism (which many here on HN already know about), what you need to do is the most important information, why you need to do it is secondary. That might be debatable to some people but that's how I view it.
IIRC (from taking journalism in high school), journalistic standards are:
Tell the most important info in the title as briefly as possible.
Repeat the most important info with a little more detail in the first paragraph.
Repeat your main point and add more details in additional paragraphs. You should be able to cut out the final paragraphs (or not bother to read them) without losing any actually critical information.
Each additional paragraph should add new information, but not be essential to the main point of the piece.
I would provide much less background information here. "What you need to do" should definitely not be below the fold. You should boil it down to:
1. This is happening 2. This is what you personally need to do about it.
Then add whatever else you want after that.
I know this is just an example, but it should set a good example.