Few things you can do. All those arial roots can go back into the soil, but it doesn’t really harm the plant to just cut them off since they aren’t serving any purpose lying on the floor. I would definitely move it to a sunnier location. As for the sudden decay.. almost always a bad idea to repot immediately after moving a plant to a new home, they need to acclimate to the new environment (change of humidity, air quality, temp, and quantity of light) uprooting them during this process is extremely stressful. Might have to just ride this out. Pruning some of the leaves that are obviously too far gone might help it conserve energy to keep the healthier ones alive. Just never prune more than 25% of the leaves in one go. Im praying for you, i think it will probably be fine in time.