Not a mixed metaphor, it’s a standard phrase.

Note buggy WHIP makers, not buggy makers.

No, it's not mixed. It's related to the saying about the people who get rich off a gold rush being the ones who sell shovels. In the buggy-whip case, it's about a company not understanding the market changing entirely to make them obsolete. The transportation market moved to cars, and so nobody needs a buggy whip.

Watch the movie “other people’s money” for the original reference

The original reference is probably Levitt's "Marketing Myopia" (https://books.google.com/books?id=Zn4foOUm3AoC). Levitt uses it to illustrate that companies should focus on customers rather than products.

Well OPM came out in 1991 so I doubt it.

https://youtu.be/62kxPyNZF3Q

Note the imprint, "Harvard business review classics." What I linked to is a 2008 republication of a book from 1975. The buggy-whip analogy also appears in a journal article of the same name by the same author in 1960. More info here: https://hbr.org/2016/08/a-refresher-on-marketing-myopia

Thanks for the detail and I should have dug deeper

Because they invested in the new up and coming thing and transferred the knowledge that applied.