From a reddit thread, it was stated that the deceased woman was of above average girth, hence she couldn't be moved/dragged up the aisle.
https://www.cnn.com/2025/02/26/australia/qatar-airways-flight-dead-passenger-body-intl-hnk/index.html
An airline traveler has spoken of his shock after cabin crew sat him next to the body of a fellow passenger who had died during the flight.
The female passenger collapsed in the aisle beside Mitchell Ring and his partner Jennifer Colin during their Qatar Airways flight from Melbourne to Doha, they told CNN affiliate Nine Network. The Australian couple were on their way to Venice for a vacation.
Ring recalled watching the crew try to revive the woman.
“Unfortunately, the lady couldn’t be saved, which was pretty heartbreaking to watch,” he told Nine.
The crew then tried to wheel the body toward the business class section but were unable to maneuver it through the narrow aisle, Ring said.
“So they looked a bit frustrated and then they just looked at me and saw seats were available beside me… and they just said to me, can you move over please?” he said. “And I just said, ‘yes, no problem,’ and then they placed the lady in the chair that I was in.”
Ring then sat next to the body for the roughly four remaining hours of the flight, he said, despite there being other empty seats on the plane.
Another passenger offered Colin an empty seat across the aisle from Ring, where she sat for the rest of the flight.
“I was really shocked,” Colin told Nine, calling the experience “traumatic.”
“We totally understand that we can’t hold the airline responsible for the poor lady’s death, but there has to be a protocol then to look after the customers that are on board,” she said.