I have been trying to install MSFS 2020 also. It seems that when it gets to a certain point in the installation process it just hangs there and does nothing. I allow what I think is a sufficient amount of time to see if the installation will proceed and then I will close it and try again. Today I am trying again and I am now up to 15 GB installed. So far so good but we'll see.
I believe that there may be issues with the ASOBO installation manager.