Mr Mahon said he was frustrated and angry at Ulster Bank after it increased his monthly mortgage payments from €150 to €963.
"I felt really stressed, but I apologise for what I did," he told the Herald.
The father-of-three had an interest-only mortgage on a second home and went into "meltdown" when his monthly payments went up by 600pc.
He said the bank refused to discuss alternatives and carried out the attacks to disable the ATMs.
Mahon said that he "deeply regretted" disabling the ATMs and was relieved that the bank agreed to accept €5,000 compensation for the damage.
Mahon, of Kilvere Park, Cypress Downs, Templeogue, had pleaded guilty to causing criminal damage to ATMs at various locations.
These included Ulster Bank, Donnybrook Road, as well as Dundrum, Stillorgan, Terenure and Ranelagh on dates between September 8 and 29, 2012.
The Donnybrook Road ATM was damaged five times, the Dundrum machine three times and the others on either one or two occasions. Defence solicitor Jenny McGeever told Dublin District Court the bank had offered to accept the €5,000 on condition that Mahon undertakes not to damage any of its property again.
The accused had got out a credit union loan in this amount and would find it "nigh on impossible" to get any more compensation, she said.
"I am hoping, in the view of the very generous and gracious approach the bank has adopted, that the court can finalise matters," Ms McGeever said.
Judge Victor Blake said the money should be paid to the bank and a receipt brought to court on the next date.
He also wanted references, and a written undertaking from Mahon to carry out no more damage. Judge Blake adjourned sentencing for two weeks and Mahon was remanded on continuing bail until July 26.
Previously, the court was told that Mahon bought a rental property in Limerick in 1999 for €80,000, and later got an interest-only mortgage through Ulster Bank, with monthly payments of €150, Ms McGeever explained.
However, in October 2011, he was "suddenly" contacted and told the repayments were reverting to capital and interest, at €963 per month. He called the bank to attempt to draw up a schedule of repayments, and "did everything he humanly could to deal with the situation in an adult and responsible fashion", but was met with a "blank wall".
He also suffered ill health and went into "meltdown" before carrying out the damage.
"He did not think the damage to the machines would be as severe as it was, and thought they could be cleaned and would be okay again," Ms McGeever said. "This is not a case of wanton damage.
"This pressure overcame him and he acted very uncharacteristically."
After his court appearance, Mr Mahon told the Herald: "I would like to warn people that switching to an interest-only agreement can result in very high repayments once the interest-only term ends.
"I realise I broke the law and caused the gardai a lot of paperwork, for which I apologise. I did not think the damage was going to be as serious as it was. I deeply regret doing it.
"I had felt the bank was being very unreasonable by not responding to several of my proposals to make a deal with them on repayments, and I got frustrated by the lack of replies.
"I've suffered depression in the past and all the stress of what happened contributed to making me ill again and I spent five weeks in St John of God's Hospital after Christmas. I'm still on medication," he said.
"The bank phoned me afterwards and offered to put me on €150 interest-only payments.
"But I told them I had managed to rent out the Limerick flat for €400 a month and we have agreed on €300 repayments on the mortgage," he said.
He said he feels angry about the State's bailout of the banks.