I've been doing this a long time. As far as I can tell, it comes down to senior leaders in software development wanting to make some sort of success story to further their own careers. It's much easier to buy into somebody else's canned success story plan. Hence the popularity of stuff like "Scaled Agile". Which is funny to me, because in practice, it's heavier than old school MS Project and Waterfall development. Even the diagram they use to summarize the concept is laughably undecipherable and complex[1]. Same reason companies latch onto 6-sigma, Clifton strengths, TOGAF, Total-Quality-Management, and so on.

I do recognize there is some actual "good stuff" in there. I'm a fan of the textual agile manifesto.

[1] https://19yko92jjsfl3euk0g1esoja-wpengine.netdna-ssl.com/wp-...