It also depends a lot on how they count these market shares. Once we go past the basic renting of CPU/Disk, it gets tricky: How far is a service still considered as part of the "cloud market". For example, renting a virtual machine to use as a desktop-in-the-cloud would count, but what about 'renting' a machine to play games? (Like with Xbox, Luna or Stadia) Same question with productivity/office services.
It is amazing how much the first-mover advantage helped AWS. I signed up for AWS in 2009 after trying GoGrid and Rackspace Cloud and just never looked at any others later on. Just this week I tried GCP and I like it much better. And Azure has a nicer geographical footprint.
Here's an example: https://www.statista.com/chart/18819/worldwide-market-share-... . The link is from Statista and aligns closely with the WSJ numbers, and it points to "Synergy Research Group" as a source for that breakdown.