The quick-and-dirty bit IMHO is that Apple has had problems with one of its data hosts - Amazon AWS. I've used AWS, Apple uses AWS, MS uses AWS, Netflix uses AWS, and Amazon Prime (video/music) uses AWS - but only Amazon Prime seems to never have problems...
Apple was recently tied to moving to Google Cloud (
http://www.businessinsider.com/google-nabs-apple-as-a-cloud-customer-2016-3), there's plenty of links out there that show MS's Outlook Cloud Services moving to Azure from AWS, and I've moved my cloud services from AWS to Azure and Office 365.
My Exchange cloud servers and email servers were hosted on AWS, along with my Outlook.com accounts - now that they're over on Azure all of my outage and downtime "issues" are done. I'm guessing that other companies are moving away from AWS because of these hiccups and outages - I'm smaller and more nimble than Apple, but I'm also guessing that they've had enough of Amazon's excuses (too?). I love Prime, but I'm not fond of AWS at this point.
As to downdetector.com - head to the home page, as I do when I suspect there's an issue with one of my cloud services. The companies nearer the top of the home page tend to be having current issues - right now, Cricket Wireless is in the top row and they've gone from "no reports" about 90 minutes ago to "12000 reports" now of outages just from performing a mouse-over of the graph on the report page - as you'd scroll down the reports page you'll see input from Cricket's Twitter feed and Facebook page. In other words, you'll see iCloud near the top of downdetector's home page is iCloud was experiencing issues. Click on any of the company logos and you'll see additional detail of what a company is experiencing, in real time...