Unfortunately I did not think of sterilizing the plant nor the media prior to repotting. I have some Physan solution on the way so will get into better habits in the future!
I presoaked for only an hour or so. Possibly could have gone longer.
Is root rot over a short period of time indicative of a fungal problem? Since 2 weeks seems awfully short for bad watering practices to rot so many roots! (and my watering practices should be OK),.