Although it is hard to kill ficus, it is possible. It is actually normal for figs to lose their leaves if they go from higher light to lower light conditions. Ficus is fussy about having its light messed with. I think you probably over watered it when it started losing leaves thinking that was the problem. Most people do that. Shifting it back again to another location, just adds more stress. Now that the stem is starting to decay it could be hard to save. The roots are rotted. You will need to cut back all of the dead roots and the dead stem. If the core of the trunk has already started to shrivel it may be too late.
If you get another ficus. Just keep it in one location. It is likely to drop every leaf if your location is darker than where it was. That is o.k. When the ficus goes dormant don't water it until it is almost dry and with most plants don't leave any water in the saucer. If you must use a saucer, put the plant on pot feet so it is raised above the saucer so it won't get wet feet. Better yet, water the plant in the sink or outside and let it drain before putting it back on the saucer.
Ficus will usually adapt to most light conditions but it does need light. The leaves would have regrown in time.
Happy gardening in Hawaii. Gardens are where people grow.