Well, let's see why it's not so funny:
1. His conversion corresponded not to an event when it would be politically expedient, but to a fire at his dacha that almost killed all his children.
2. When he was KGB, there was an internal debate in the KGB as to whether or not state atheism hadn't been a hideous mistake (as reported in a biography of Putin in the Atlantic Monthly about a year ago).
3. Spiritually perceptive monastics regard his conversion as genuine.
4. He is the only Russian head of state to ever make a pilgrimage to Mount Athos.
5. He has instituted Orthodox Christian education course in Russian state schools.
6. He regularly makes his confession to monastic priests and attends Divine Liturgy, participating not perfunctorily as Yeltsin did, but with all the proper prayers and gestures of fitting Orthodox worship.
I find his attempts to play balance-of-power politics vis-a-vis the US, trying to use the Iranian lunatics the way Britain used Prussia as a counterbalance to France centuries ago, short-sighted, and suspect it is against the interests of Russia as well as the US.
But all the powers that played balance-of-power games in Europe in the old days were Christian nations, often with pious monarchs.
I'd not laugh at Putin's faith on the basis of his past, or his attempts to look out for his own country's national interests.