The clear answer is that corporations paid a lot of money for this change. Google's AWS's Microsoft's all wanted sysadmin to go away and devops to be in as a way to sell their services. Read more into it
Why so conspiratory. Yes marketing is one aspect of it. But then again a massive amount of sysadmins are required to manage the cloud ops and very often you need a full time devops person on site to replace the sysadmin. In other words efficiency might have gone up but the it budgets did not go down. All in all the world became better with devops for everyone but the ones whos jobs are not as relevant as they were yesterday.