Can overheated exhaust result in engine damage?

Hi, my first post hoping to get answers to a puzzling question. 2000 Chev 3500 with bus body, used by church, reportedly running fine. Pulled over due to sick passenger and smelled smoke. Lifted hood and found flames, used fire extinguisher and had vehicle towed to mechanic who said the heater hoses from upfitters fell onto exhaust manifold and insulation caught fire, burning heater hoses, spark plug wires & evap hose. Those were replaced. Next, engine determined to be knocking and replacement recommended. Found hoses just replaced melted again. Theory is now that exhaust blocked causing manifold overheat resulting in melting/fire. Questions are (1) could the fire under the hood cause the engine failure? (2) Could blocked exhaust result in engine failure? Pls explain (I am a novice) and thank you!

The heater hoses melting should have resulted in coolant loss and overheating, which can trash an engine in short order.

Never heard of a blown engine from an exhaust issue.

Yes - Plugged catalytic converters can cause Heat damage, do a catalytic converter back pressure test, also make sure both coolant fans are working when the HVAC is on cool Max.

Thank you.