This isn’t really a surprise. Most modern battery tech has a hell of a lot of energy in it which is what we desire to support long run times. It only takes a manufacturing error or some physical damage to let all that out pretty sharpish. This is usually a violent incendiary process on LiPo cells.

I doubt the battery in question was overcharged or this was because it was left on charge, but because it was faulty or damaged.

This one is a relatively small one: https://youtu.be/bqcX1AjdxSw