答案:Because he found that the little man was not clever and had nothing to teach him.
根据最后一段倒数第1-3行:
If he did, then these little people of the future were not very clever. I was very disappointed. 'These people have nothing to teach us,' I thought.
如果他知道,那么这些未来的小人就不太聪明了。我非常失望。‘这些人没有什么可教我们的,’我想。
可知答案为:Because he found that the little man was not clever and had nothing to teach him.
(注意结合原句进行归纳、总结。)