Sorry for the loss.

It reminds me of how my camellias look when they have lack of water but I may be impossible to know now exactly what happened when.

Heavy rains should not have been an issue if the soil drains well. You can detect this when it is happening if you test the soil: insert a finger to a depth of 4". If the soil is wet, that can be a problem if the rains continue for a long period of time. You may need to force the water away from the camellia (might need help of a landscape company for things like this).

The problem may have occurred before the winter rains that you mentioned as I do not see any flower buds. If it never bloomed then there may have been a problem at the time that it produces flower buds in the Fall. If it bloomed then the problem happened after that.

Thanks for your comment. There are buds but they never opened. Following the advice of a tree doctor, we dug out around the root to let it dry out. And we are planning to divert any more rain water away from the roots. I hope this works.

Good luck, emmang. And a heck of an ordeal! I too had to have a landscape company do some water diverting work on my back yard to correct similar problems 10+ years ago. Back then, I lost an Alice Oakleaf Hydrangea when El Nin~o dumped unheard of rains from March thru July. We were getting gobs of rain (1-3") whenever it rained and it rained more than once a week. Seeing the sun was actually a surprise when it happened and a Gardenia that I had bloomed twice on that year when temps went up and down in the summer. Really weird weather.