collapse into something
1. Lit. to fall down into something with suddenness, as if out of energy. She was so tired, she collapsed into the chair. Juan collapsed into a chair and fell fast asleep.
2. Fig. [for someone] to fall into a particular kind of despair. The poor man collapsed into a deep depression. Scott collapsed into his own personal brand of grieving.
collapse under someone or something
to cave in under the weight of someone or something. The grandstand collapsed under the weight of the spectators. The bridge collapsed from the force of the flood.