DPI is not as important as you might think. And DPI can be seen this way, or that way :)

Images are usually not saved with a DPI specification. Or with a size specification for printing. An image has pixels. That's it usually.

If you load an image, then it's up to the software how it interprets the number of pixels available (which in your case Photoshop did). If you want a different value (size or DPI) then the other value changes accordingly. Because the image has only a certain number of pixels, which you can distribute in different densities (DPI) on an area (image size). If you change both parameters at the same time, the software must either take away points (reduce) or invent some (enlarge).

https://snapshop.cam/dpi/

https://en.wikipedia.org/wiki/Dots_per_inch

---