Yes, Greece was predetermined to "get hit" as you put it. There was no need for it to get this bad, though. A number of US states (e.g. Mississippi) have a similarly inferior economy compared to the union average, but the situation is stable thanks to federal fiscal policy.

I can only speculate about what motivated Greece to join the Eurozone.

My guess would be that Simitis' believed his reforms (Eksynchronismos) fundamentally transformed the Greek economy. Politicians take bold action to ensure their legacy, and it must be tempting to go down in history as the man who fixed his country's economy and led it down a road of mutual prosperity.

Perhaps he understood the economic risks, perhaps he didn't. He was certainly warned by economists. Perhaps he simply didn't believe the rest of the Eurozone could be this obstinate and cruel. It's hard to say for sure. We certainly can't take the politicians' words at face value.