Only because they found it much more effective to "collaborate" on the regulations such that they'd be allowed to label opioids however they'd like and addict millions of people in one of the biggest health crises in the history of our country.
Separately, yes, there are also instances of straight-up corruption. It's totally divorced from reality to suggest that collaboration is "only because" of corruption though.
NIH researchers (and their funders, US taxpayers) should be getting paid more in royalties from commercialized research.