There is no legal way for the EU to throw Greece out of the Eurozone without them agreeing to it.
Greece could default, revert back to their national currency or keep the Euro currency and STAY in the EU at the same time.
He declared what he wanted to do, this of course meant that he had to convince the other EU elites which required open ended negotiations in good faith.
I'm sure that no one in their right minds in Greece believed that Tsipras simply could dictate something to Brussels.
Apparently negotiations failed, that can always happen, but at least he tried.
Also It is never ridiculous to let the people of a country decide especially on hard questions after the facts on the ground have changed. I never understood the mindset of people who loathe on democratic decision-making.
You seem to believe that there never was the possibility to reach a mutually beneficial agreement to begin with, and Greece should simply roll over and let their economy contract another 25% after it has already contracted 25% in the last years.
If this were the case (I disagree) then maybe it's for the best to exit the EU and work with the Russians and Chinese on building a better future for the Greek people.