Recent Bootcamp Experience (Curious WHY this happened)

I recently tried Bootcamp for the first time and it actually broke my MacOS partition. Thanks to help on this subreddit, I was able to reinstall MacOS with all of my data, however, I would like to try again so I'm looking for WHY this happened. I downloaded the Win 10 iso and had bootcamp partition about \~50gb on my drive (whatever the minimum was). I set up windows but the bootcamp "switch to MacOS" wasn't working (it couldn't find the partition). After restarting and using option as well as cmd-R, I was able to restore the broken MacOS, but the windows partition didn't work after that. Making it worse, BootCamp never recognized the existence so I had to manually delete and reabsorb the partition. If anyone has had a similar experience, pls share what you were able to do to fix it! I'd definitely like to try this again. My end goal is creating a portable SSD I can use on both my Mac at home and Lenovo and work, and this is the first step in the process. Thanks in advance!