That is not the problem unfortunately. When I open lightroom mobile it shows the worse version also. I have tried exporting it from desktop and from mobile onto my saved images on my phone. It exports it weird every time.
Another thing to add. The picture looks grainy like the one in the left when i look at it in mobile as well, up until i press and hold it to reveal undedited version, then when i let go, it self corrects all the editing back on and looks correct! but if i swipe to another picture then back to it, once again looks grainy and incorrect.
You're running into a limitation of the web sharing feature of Lightroom cloud. It uses fairly low quality previews. This is a heavily edited image with what looks like a very strong shadows setting and probably some local edits to lighten the people. This will definitely accentuate the problem. Make sure you optimize the noise reduction on this image and only touch the noise reduction and sharpening sliders when you are zoomed in to 1:1 zoom. If you change noise reduction and detail sliders while zoomed out, you are likely to make decisions that result in problems you will only see in exported files or in previews such as this