Billionaire retailer Gerry Harvey has launched radio ads defending Optus, as he said the huge “pile-on” of the beleaguered company over last week’s outage was “beyond stupid” and “over the top”.

The commercials feature the Harvey Norman owner saying Optus was “getting a raw deal”, and that the IT meltdown could happen to any company.

It came as Optus finally revealed the reason behind the communications outage that caused havoc for millions of people and businesses across the country.

The Harvey Norman ad starts with Harvey, 84, stating: “Optus, Optus, kick them when they’re down! Really? I thought Australians were better than that.”

He continues: “It could happen to any company. It could be your turn next time. For what it’s worth, Harvey Norman will support Optus.

“Yes, we will support Optus. If you think Optus is getting a raw deal, then you think like us.

“Need a new phone? It’s an Optus deal at Harvey Norman. Tell them Gerry sent you.”

In an interview, Harvey told Perth radio station 6PR that software problems like that that shut down the Optus network for 10 hours last week was not the CEO’s fault.

He said calling for the heads of CEOs or other executives was an over-reaction.

“This is ridiculous – this could happen to anyone – it could happen to Harvey Norman tomorrow and then they’d call for me to be sacked. We don’t run the IT department,” he said.

“Why does everybody suddenly want to attack … the CEO and the chairperson – they both got to go – this is ridiculous.

“Then politicians piled onto it, the media piled onto it. It’s way beyond stupid.”

Harvey called for perspective, saying the Optus network collapse “lasted 10 hours – it didn’t last 10 days”.

He said he decided to run the radio advertisements “because I thought the overwhelming response from the media and politicians was way over the top”.

“When we see someone being treated unfairly why shouldn’t we step up and say ‘What is going on here?'”

Harvey said it would be a “tragedy” for Optus chief executive Kelly Bayer Rosmarin to be sacked over the nationwide outage.

“I suspect they won’t, I hope they won’t. If the person is incompetent then sure,” he said.

Harvey said his company also lost money because of the outage and was unable to communicate with its customers about deliveries. But he said “you can’t expect compensation every time an accident occurs”.

Optus said in a statement on Monday the cause of the outage was known and it had taken steps to ensure it wouldn’t happen again.

“At around 4.05am Wednesday morning, the Optus network received changes to routing information from an international peering network following a routine software upgrade,” the company said.

Optus said it had made changes to ensure it did not suffer another disastrous outage.

“These routing information changes propagated through multiple layers in our network and exceeded preset safety levels on key routers which could not handle these,” it said.

“This resulted in those routers disconnecting from the Optus IP Core network to protect themselves.”

The time taken to restore the system was longer than anticipated because some of the routers needed to be physically rebooted, requiring Optus staff to be deployed to sites across the country.

“The restoration of the network was at all times our priority and we subsequently established the cause working together with our partners,” the telco said.

“We have made changes to the network to address this issue so that it cannot occur again.”

Suggestions the outage was caused by a software update were dismissed by Bayer Rosmarin last week.

“It’s highly unlikely, our systems are actually very stable,” she told ABC Radio Sydney last Wednesday morning.

-with AAP