RX3 chain issue

[Juanca]

Hello friends.
last night I was starting off a traffic light and suddenly felt like the back tire was flat, so I pulled over and noticed that the tire was fine but the chain mas misplaced on the back sprocket.
I tried to putting in place but it was way too tight, so I ended up calling insurance and get a tow truck to my house.
I am going to have a new chain and sprockets change, but wondering why this happen, if you have any ideas let me know.

Thanks