They were in the union, kept their own currency and had exemptions from a lot of EU rules.
Now they fucked up royally out of pure arrogance and some ill-advised nationalism.
Good luck.
I suspect that the grandparent is joking, doing the "why did the EU do this to the UK?"
The joke is that brexit issues are never the UK's fault. Along the lines of https://knowyourmeme.com/memes/who-killed-hannibal
UK's entire chain of options were known to everyone with half a brain even before Brexit started. Described succintly in this chart: edit see first chart on House of Lords page here: https://publications.parliament.uk/pa/ld201719/ldselect/ldeu... end edit and explained very briefly in this video: https://www.youtube.com/watch?v=agZ0xISi40E
As an EU/UK citizen living in the UK - I'm okay with that. The EU signed a contract with a 3rd party company and they are requesting delivery on their goods.
For Greece - I think the level of corruption in the Greek market was pretty obvious so I'm not so too bothered by the "wrecking". If they followed the laws and didn't steal money - they would have been okay.
They also said they will get the deficit under control in 2 years and a few months later said they would most likely default.
They had massive tax evasion problems (e.g. corruption) and one of the lowest retirement ages in the EU.
I'm really nor sure how you see corruption given that the government took out loans which it had no way of repaying even with 5% YoY growth. The simple fact is they were fiscally irresponsible. It's a common pattern in the Balkans to just do what is needed to win the elections without thinking of how the country is developing and what is the right course. It stems from the corruption of the political system.