Some of the landlords in Ireland with one property are accidental landlords. They never wanted to become landlords but their time of purchase, the subsequent financial crash and making starting a family (kids arrived etc) forced their hand.
They now have the chance, even if it's just breaking even to get out and have less hassle in their lives.
Important to remember, that they might be breaking even, but cash flow wise, the property/rental could in all likelihood have been a drain on their cash flow. A property with a mortgage of say €1200 a month and it was rented for say €1,600 a month. That €1,600 a month might have €300 expenses a month between insurance, property tax, management fees etc. The tax man at 50% would be taking say another €600-€650 a month, so the landlord/family owning the property are getting €650-€700 into their hand but paying out €1200 a month on the mortgage. So keeping the property/rental is "costing" them €500 a month.
Yes, I know people will say they are paying down capital and will be left with an asset, but these people never wanted to be landlords in many instances to begin with, so they would rather have the extra €500 in their pockets each month at a time in their lives when they may have childcare expenses, holidays, enjoying life with kids etc.
The conversation you're replying to was LL having doubled the value of the property are getting out. There would be no mortgage, and the value of the property is still rising. There would be no cashflow issue.