Greece had the alternative of dropping out of the Euro and defaulting on their debts but even Syriza, a left wing party, when faced with that prospect, balked.

Greece's fate was sealed when they joined the Euro and started borrowing huge amounts of money that they could never repay, whilst also not carrying out structural reforms to improve tax receipts (like reducing some of the tax evasion in the country)

Their government appears to have decided that this path is "least bad". Not sure that I'd agree but I'm not in Greece to see the options first hand.

Edit: as I'm getting downvotes, I'll provide references :)

https://www.theguardian.com/world/2015/jul/03/greece-overspe...

or maybe

https://www.bbc.co.uk/news/world-europe-16834815