XD Cummings Low Pressure Turbo Replacement

Put a deposit on a 2018 Titan XD SL w/Cummings & 30k original miles. The XD sold new on Dec. 31st 2018 at a dealership in Texas. Truck is for sale at a very reputable dealership, there are dozens of dealerships owned by the parent company throughout the South East. The check engine light came on soon after the truck arrived at the dealership, so the dealership sent the XD to a nearby Nissan dealership for service. I have followed up with the Nissan service manager weekly during the course of the past month as Nissan work the locate & resolve the issue. After replacing several parts without success, Nissan replaced the low pressure turbo. Nissan dealership service manager confirmed the truck is 100% stock, with no modifications. Nissan service manager confirmed replacing the low pressure turbo resolved the issue. My concern going forward is “what caused the low pressure turbo to fail”? The XD original factory warranty covers it through Dec. 2023, and I would purchase an extended warranty if purchased. It would be great if someone could confirm why the turbo went out on a 30K mile Cummings? Any suggestions or recommendations are welcome.