Yeah that's some pretty widespread spalling on the garage deck. Regardless of what went wrong, I'd be surprised if rust jacking or just plain section loss of the rebar wasn't a principle factor behind the collapse. All of that rebar has just been rusting for an additional 3 years since those photos were taken and it looks like the corrosion was already pretty spread out at the time and no one did anything to address it.

Tyler Ley has dozens of videos on the topic, I know I've seen a great overview of concrete deterioration but he's got so many videos I can't find it. Here's a intro to concrete corrosion though that explains some of it.

https://www.youtube.com/watch?v=mOCJFCaXN0s