A better characterization would be "the first mover fighting off large competitors". (Unless I'm misremembering) There was no direct equivalent of Dropbox at the time. I had tried everything from Skydrive to rsync. Dropbox solved a real problem with storage at that time.

(I don't use them anymore because they are too expensive but good for them that they are able to charge so much)

It's almost all spin. Enterprises are not adopting Dropbox (or Box) at any real scale because of privacy, security and control of data concerns. It's why you won't see any business that has data compliance requirements (such as banks) listed as a reference customers. The opportunity for large businesses to use Dropbox is very limited.

Where can you find these details on the decisions they made and the effects on their survival? Would be an interesting read.