You should never keep decrotive foil or anything on the pot that prevents drainage. Orchids don't like their roots to sit in water. Your plant did have lots of roots and looked like it did need to be repotted. Since you cut off the old back bulbs, the roots that were connected to them probubly will die or have died. But orchids like to be snug in their pots. The part with no green on it won't live. If you would of left the back bulbs on you could of divided the plant and gotten the back bulbs to grow new growths. Many orchids can be propagated this way. The growth that popped off I'm assuming was the one that looked kind of brown? It might of rotted at the base from the pot not drying out with the foil on it. But new growths can be very fragile so you have to be careful with them.
If I were you I would cut off all the dead squishy hollow roots and repot the piece with the green growths. The white fungus could be growing on dead rotten roots and root rot is from the roots not drying out fast enough and sitting in water.
Cymbidium pbulbs do look like they are dead after they loose their leaves but they are not. It takes a while for them to shrivel to almost nothing compared to what they were before they are completely dead. My Cyms have leafless back bulbs too but I leave them on. Of course you can remove some if there are more leafles pbulbs than ones with leaves but you shouldn't remove all of them. If your plant has almost no healthy living roots left from sitting in water, the leafless pbulbs could of been really dried out. When an orchid has dead roots from root rot it can't take up water so it gets dehydrated just like if you didn't water it. If that has happened, the plant would of used the stored up energy and moisture in the back bulbs to nourish the newer growths. This could of happened if you watered the plant while still keeping the decorative foil on the pot.
If your orchid doesn't make it at least you learned something.
Everyone kills orchids when they are learning how to care for them. I know I have killed my share! Orchids are easy to find. You can find a variety at the grocery store or big box store so buy another one if this one doesn't make it. Heck buy another one anyway! Good luck!