I don’t know if this will help people here but in my case this appears related to xbox networking within windows settings > gaming xbox networking.
Specifically the part that says xbox live multiplayer. It appears that the NAT type was saying blocked for me occasionally and running the ‘fix it’ option, then check again allowed msfs to start without this insta ctd.
I have to add that this was never an issue until recently and most times I have to run this ‘fix’ prior to starting msfs.