The screen of modern iPad Pro has an extremely wide dynamic range. iPad Pro models that feature an OLED screen have a particularly wide dynamic range - typically 1,000,000:1 - these being ideal to view HDR video and photos that capture deep shadow, very bright highlights - and everything in between.
Bright ambient lighting can drown shadow detail, particularly in movies that are presented in HDR formats - often requiring that the viewer reduces the ambient lighting to a level comfortable to watch the content - or adjust playback settings within the App being used to view the content.
Within the App that you using, look for an HDR (High Dynamic Range) setting - and turn this OFF.
The dynamic range of many "standard" LCD screens are usually much more limited - often in the region of 1500:1. As such, the brightness range between dark and bright scenes is compressed, such that you can see more of the scene in brighter ambient lighting conditions - but at the expense of lost shadow detail and suppressed bright highlights.