What would make a vo stop starting when put in gear after losing the rear exhaust assembly?

My 240 sedan lost her undies from cat all the way back to tail pipe. Both mufflers and pipes just fell off on hyway...of course it was night so heaven help whoever was behind me when the whole thing dropped off.

These things only happen to me on weekend nights when there's no place open. And of course I was on my way w/ my dog, 2 cats, and packed front to rear and on the roof w/ stuff!

I pulled over and called for a tow back home. I sat for 1-2 hours waiting, turning engine on to put on blinkers for passing cars, and off to save my ears and battery which is new but had just needed a jump a couple of weeks ago thanks to my stupidity and an interior light left on.

I decided to pull the car further from the traffic. Turned over again just fine, put her into drive, started to move and she stalled and hasn't started since. Chugs like she wants to start but will not completely turn over.

I'm about to get her towed to a vo mechanic that I have never met or used or know. They only service and sell used volvos so I hope they are ok. They were game to guess-tamate the rear exhaust assembly over the phone at a price comparable to my tried and true mechanic who's sadly 200 miles from here.

I just want an idea of what made my car not start so I'm prepared beyond replacing the rear exhaust assembly!