Rather than becoming this over time, Scrum slotted into existing teams and practices that were already heavily into rigid project management. The same teams that adopted Scrum were previously using Waterfall or 6-Sigma or some other such prescriptive framework. Agile showed up, got a lot of buzz, and then Scrum came along to sell the buzz to big institutions with entire departments of professional project managers.

Were the creators of Scrum hopefully trying to introduce flexibility in the guise of process, or cynically cashing in on a trend? I don't know; all I do know is that Big Software switched from $old_process to Scrum around 2010-2012, and medium-sized companies seemed to follow in the middle of the decade.