I purchased my first Bougainvillea and need help understanding the life cycle of this plant's leaves and bracts/flowers. The first photo shows the plant when I purchased it from a Home Depot. the bracts were in full bloom and the leaves were plentiful and healthy. I brought it home and watered it every few days, leaving it in the sun. I did not change the soil and it is still in the original plastic garden container. Immediately the leaves and bracts start to die, and the second photo shows how entire stems were bare naked. The plant looked like it was dying. I increased water to the plant and added some Osmocote. Just three weeks later, now the plant is covered in new leaves and looks incredibly vibrant. That is the third photo.

What is going on here? What caused the plant to lose all leaves? Was it a lack of nutrients or water or both? Now after I supply nutrients and water the leaves instantly return, but there are no bracts. Clearly, I do not understand this plant's habits. I want the flowers/bracts. How do I get those?