Thought you said tax dodge there for a minute
Not really, there could be any number of reasons for it - people are entitled to transfer or restructure their interest in a property whatever way they see fit.
It didn’t make sense even on a basic level, without looking into the parties involved. Nothing that sold for €1.255m in Dec 2018 would have sold in May 2020 for €1.00m (20% discount) - a May closing would suggest a Feb/March sale agreed date assuming around one month for exchange of contracts and a further month for closing. Covid was only taking hold in March, so no sane person would have dumped their recently acquired property for a 20% discount.
The moral of the story is that prospective purchasers should be careful of what comparable sales they use, or else they might get unrealistic expectations. Anybody looking at that sale and trying to use it as a comparable to establish a value for other similar properties would be misleading themselves and not doing themselves any favours! Anything that was not actually on the market yet appeared in the property price register as having transacted is an obvious red flag. This one actually has a for sale ad online, but it’s possible (I can’t say for sure) that ad is from the December 2018 sale but still online given the asking price is in or around the actual sale price from that time. Some ads linger online for years.