Microbes need nutrients to break down the mulch. That’s why in JADAM mulch (aka unfermented compost) is added in the autumn, or several months before planting. Finished (aka fermented) compost may be added a few weeks before planting instead.  

The reason the plant in the mulch flowered so fast is because the stress of low nutrients caused it to go into reproduction. It died soon after for the same reason. Similarly, a stressed tomato plant might produce fruit faster than a happy tomato plant, but the happy tomato plant will usually live longer.