Monsoon air is basically 80 - 95% humidity. Water evaporates a way slower.
When clothes are still damp for more than few hours, microbes that are already in the clothes and those present in air start multiplying quickly !!!
Mildew is a fungus that thrives at >65% humidity. It doesn't need sunlight just the moisture !!!
The misty smell is literally microbial volatile organic compounds released by this fungus.
Some odour causing bacteria which live on our clothes, start producing smelly compounds when clothes are wet !!!
Clothes hung in humid rooms reabsorb moisture from air. If these clothes are folded, they trap dampness in middle layers. It is the perfect incubator for microbes !!!
If clothes are smelling mushy, rewash with hot water and vinegar, then dry completely as much as possible !!!