1) The major US Economic Depression must have had some impact.
2) Kodak abandoned film advertising and promotion. Adding fuel to the perception that, "no one makes (or uses) film any more".
3) Kodak should have bought Adobe
4) Kodak should have competed with Xerox in the early days and owned that "imaging" market.
5) Kodak doesn't realize they are in the industrial coating business, not the "picture" business. They should have leveraged those coating capabilities into new products beyond photography.
* Imagine if Kodak invented a way to coat automobiles and eliminate liquid paint and all the associated hazards *