Many people tend to like muscle training, but they will collapse and get fat without training. Muscles never get fat. Muscles (lean muscle tissue and fat) (fat tissue) are completely different and will not transform into each other. Without training, muscles will only slowly shrink and become smaller, while fat is still fat, so many people think that muscles will become fat without training.
When you don't exercise, your body will naturally consume less calories and basal metabolic rate. If you burn the same amount of calories as during training, the extra calories will naturally accumulate into fat. So if the diet is properly controlled, it will not rebound.