Peter Box, 78, put the small side unit on the stairlift to help take its weight as he moved it. He then decided to climb up the steps alongside to support it.
But an inquest heard that when he got to the top of the stairs he overbalanced as he tried to lift the unit off and fell all the way down, banging his head on a radiator at the bottom.
Mr Box was taken to Rotherham District General Hospital after the fall on September 21 this year but medics found he had suffered a serious head injury and several broken ribs.
Despite receiving treatment his condition worsened and he died four days later.
His widow Gwendoline Box, a former care assistant, of Black Carr Road, Wickersley, Rotherham, told the hearing: “I think it was just purely an accident. That’s my opinion.”
She added: “I think he was trying to balance the small cupboard on the stairlift and manoeuvre it at the same time although he wasn’t sat on the lift.
“He got right to the top of the stairs.
“He was juggling to try and lift it off when he toppled backwards with the unit on top of him right to the bottom of the stairs.
“He hit the back of his head on the radiator.”
Mrs Box said her husband, who was originally from Romford, Essex, was conscious for a few seconds then passed out and she dialled 999.
Doctors at Rotherham Hospital gave him a brain scan and found a bleed in his head then a few days later said they had found another bleed which was puzzling, said Mrs Box.
She told the hearing: “As far as I can gather it wasn’t caused by the accident, it had been there previously.
“But he had never had another fall at home although he might have had one outside and didn’t tell me, I don’t know.
“He wouldn’t want to worry me.
“He had recently acquired a little invalid scooter. He had only had it for about three weeks.
“I’m just wondering if it happened when he had been to the shops.
“I just don’t know where this other bleed came from. He never told me he had a knock or anything.”
She said her husband was an extremely independent man and said of his moving of the furniture: “He wouldn’t think he couldn’t do it.
“He wouldn’t ask for help from anyone.
“He was an independent person and a handyman. He thought he could go on like he did 40 or 50 years ago.”
Mrs Box said that after the fall her husband was “very drowsy” and added: “A few hours later he deteriorated and went unconscious again.
“They took him for another scan the following day and there was no change.
She said his condition went downhill and he died on September 25th.
A pathologist who examined retired scaffolder Mr Box after his death said he had died from a combination of the effects of the two bleeds on the brain.
He had also suffered a stroke but the pathologist said it was likely that came after the injuries he suffered in the fall.
He had suffered several fractured ribs on his left-hand side as he tumbled down the stairs with the cupboard on top of him.
Rotherham coroner Nicola Mundy recorded a verdict of accidental death.
She told Mrs Box: “I don’t think there was any naturally occurring brain incident that made your husband suddenly fall backwards. It was him trying to get the unit upstairs.”
The coroner added: “He was endeavouring to get a unit upstairs, and in an effort to do that he was trying to utilise the stairlift while he walked up trying to balance it.
“He was struggling to lift the unit off the stairlift and toppled backwards and fell downstairs hitting the back of his head on a radiator.”