Console downloads are frequently slower than the same connection managed on a computer, and it is usually deliberate. While a game is running, the console reserves bandwidth and processing for gameplay and slows the download to a trickle.
Rest and standby modes vary too. Some consoles pause downloads entirely in low-power states unless the setting that keeps them running is enabled.
Hardware plays a part. Consoles placed in cabinets and connected to the slower Wi-Fi band frequently cap out far below the line's capability.
Finally, large updates are not simply downloaded: they are also copied and rebuilt on the internal drive, which is why progress can appear to stall near the end.