关于哈利波特中的一段翻译,不太明白

关于哈利波特中的一段翻译,不太明白
中文翻译：家住女贞路4号的德思礼夫妇总是得意地说他们是非常规矩的人家.拜-托,拜托了.他们从来跟神秘古怪的事不沾边,因为他们根本不相信那些邪门歪道.
原文：Mr. and Mrs. Dursley, of number four, Privet Drive, were proud to say that they were perfectly normal, thank you very much. They were the last people you'd expect to be involved in anything strange or mysterious, because they just didn't hold with such nonsense.
为什么翻译成中文的时候把They were the last people……这一句话翻译成他们从来跟神秘古怪的事沾不上边,感觉翻译的很奇怪,明明原来的意思是他们是你能最后期待跟古怪神秘事情沾边的人.为什么译者要这样翻译呢?
还有啊，They were the last people……mysterious能不能算插入语，因为原文的逻辑是他们说自己是规矩的人家是因为他们不相信那些邪门歪道，似乎跟这一句插入语没什么必然联系，对吧？