The PS1 was basically a repackaged project from their Nintendo partnership. They didn't really have time to develop proper development tools for it, and almost as a consequence of that, the development environment was very scrappy - it hooked into existing PCs and included a bunch of libraries that developers were somewhat familiar with using. As a result, the developer toolset was relatively easy to use. It allowed many developers to get started making 3D games and experiences very quickly. This caused developers to be swayed to the Playstation ecosystem early, and drove all 3D resources into Playstation development away from the Sega Saturn, which had the typically convoluted development environment from past generations (further exacerbated by Sega bolting together additional chips onto the Saturn to try to compete with the PS1).
PS2 came along, and Sony was already deviating from their easy to use console debut. Their "emotion engine" was notoriously hard to develop for, but Sega with the Dreamcast didn't have the legs to compete with Sony's momentum from the PS1, and quit the console business. Nintendo also screwed the pooch that generation with the Gamecube and Microsoft didn't seem to be a threat with the Xbox which was a major flop in Japan.
Along comes PS3, and Sony goes full speed ahead on their hubris - expensive console, impossible to develop for, an architecture somewhat reminiscent of Saturn's hodge podge of chips. At this point they completely lost their way from what made the PS1 set them up for multi-generations of success.
It's interesting to consider how the ecosystem matters when developing these hardware products, and how easy it seems for companies to lose sight of that.