Nikon makes cameras, lenses, medical and consumer lines, but their market cap is roughly 529.86 billion JPY
So the Canon company is a lot larger.
Sony itself is even more Juggernaut. They make a ton of things and market cap is about 12 trillion yen.
Market cap doesn't tell the whole story, but you can understand why Sony and Canon are referred to as "juggernauts" compared to Nikon.
On the imaging side of things, I think the current rise of casual videography is eating Nikon alive.
Even if you don't have youtuber / OF aspirations, almost all cameras that sell today need to have some kind of video mode. Cell phones excel in this segment, being able to take short videos of people just walking around doing their day-to-day stuff, having fun, working, etc. In my opinion, video has taken the place in society that taking still photos had back in the 1980's and 1990's.
Anything that goes viral these days is a video uploaded on worldstar or youtube or tiktok or instagram etc.
Canon and Sony both have pro-video recording line (used in TV/cinema industry), and I think what they did was cross pollinated the video knowledge very early on with their consumer digital cameras.
Nikon has always been a "stills first" camera company. They did put a lot of video features into their cameras, but it wasn't enough.