It's nice to see that a journalism degree is universally applicable.
What you describe is basically an inverse pyramid news article.
Hook Lead Background News
Putting it into 5 sentences is where the art comes in...
I do this too, especially when emailing people who I believe are unable or unwilling to read a long email. It feels weird and unnatural. I'm not sure if the people I'm sending to appreciate it, but I know I can very easily become very verbose, and which details are important is very context sensitive and sometimes non-obvious.
At the end say "[more detail below if needed]". Draw a line in the email ===== and include more detail below that they can dip into if necessary.