A lot of the commentary on Greece fails to see why the Greek No vote changes anything. This view tends to see the stance of the Eurozone group as simply expressing their own voters’ preferences which will not be changed by what happened yesterday. Here is an alternative reading.
It starts from a simple observation. The Troika will get far less of its money back (if any!) if Greece is forced out of the Eurozone. (I say forced out because Greece does not want to leave, so Greek exit is first and foremost an ECB decision: if you think otherwise read Karl Whelan and Matthew Klein and Paul De Grauwe. ) That is why creditors are generally weak in negotiations of this kind. Things are different in this case only because the creditors include the ECB, and Greece wants to stay in the Eurozone. The Troika has played this for all it is worth. They were relying (you could say gambling) on the Greek people, one way or another, deciding that they would agree to the Troika’s demands because they feared Greek exit more.
So far this strategy has failed. First they pushed Tsipras further than he could possibly go, hoping perhaps that Syriza would collapse in recriminations. Tsipras’s response was a unifying referendum. They then gambled that Greece would say no, and they lost that too. Tsipras continues to offer the Troika the chance to be more reasonable. He followed the referendum not with triumphalism but by removing his finance minister. This was both a signal - I really want a deal, even though it will in all probability inflict further (unnecessary) pain on Greece - and a lifeline, because the Troika can now say that an important obstacle to a deal has been removed. (An obstacle, because Varoufakis was too open - something politicians and much of the press hate - and too honest about the other side’s lack of economics.)
Now the Troika seem to face a simple choice. Agree a deal and get a little more heat from your political opponents at home for ‘giving in’, or force Greek exit with the risk that you will get a lot more heat when Greece defaults and people realise you have lost all their money. If they are really just interested in getting as much of their money back as possible, it would seem crazy to throw away their best card by forcing Greece out of the Eurozone.
Of course rationality may not prevail, or interests may be rather different. The IMF may continue to be an unhelpful nuisance. (If you think my criticism of their role was harsh, read this from Peter Doyle.) Some within the Troika will be happy to go for Greek exit because they think nationalist sentiment can overcome any kickback from the subsequent Greek default. Others may fear a deal may encourage anti-austerity sentiment in their own indebted countries.
Unfortunately there is a third possibility, which is probably the worst possible outcome. To prevent any loss of face, the Troika may continue to gamble, waiting for days or even weeks, and watch ECB pressure, together with reluctance by Tsipras to introduce a new currency, gradually bring chaos to the Greek economy. Only then will it negotiate, allowing any deal to be portrayed as the result of desperation by the Greek government. In which case, recent European politics will have reached a new all time low.
 Postscript: Martin Sandbu provides a very clear account.