The entire digital camera industry was worth about 18 billion in 2017[3]
Even if they captured 100% of the market (which would have been basically completely impossible), it would have been a massive disaster for them as a company, and to the hundreds of thousands of people they employed in photo processing.
[1] https://www.photosecrets.com/the-rise-and-fall-of-kodak
[2] http://www.in2013dollars.com/1993-dollars-in-2018?amount=310...
[3] https://www.researchandmarkets.com/reports/4514578/digital-c...
Yes, cellphones contain a camera, but the similarities end there.
Smartphones replaced compact cameras for a huge portion of casual photographers but as you point out it's not like camera makers could easily pivot into making smartphones (some of them probably could have if they had anticipated the trend enough, but by the time the iphone came out it was probably already too late to catch up).