Why was the elephant mad?

The elephant wasn't mad, he was in his "must" or "musth". This condition is a normal trait in male elephants when their reproductive hormones peak, and as a result of their raging hormones, they become very aggressive. The bull (male elephant) was in his must and had escaped its chains.

It was not, of course, a wild elephant, but a tame one which had gone "must." It had been chained up, as tame elephants always are when their attack of "must" is due, but on the previous night it had broken its chain and escaped.