Things the business got wrong? Try Michael Jackson's most recent record contract (or the one before, if that's the one I'm thinking of - I really don't pay much attention to that sort of trivia). Megabucks in outlay, mini-bucks (at least by comparison) in returns.
And the second category?
Things that slipped under the guard over the past fifty-something years?
Any number of examples that spring to mind. Let's highlight a few.
Elvis Presley.
The Beatles
Robert Zimmerman, at one stage known as Hammond's Folly but famous worldwide as Bob Dylan.
San Francisco 1967.
The first wave of punk rock.
That's a few to start with. Some things that slipped under the industry's guard, of course, ended up as corporatised crap once the biz identified the bandwagon and jumped on.