为什么用两个介词in in

Long hair for men came in in the sixties. 

男子留长发在六十年代流行。

这个句子为什么有两个介词 in？是不是打错了？

解答如下:

第1个in与came构成搭配"came in 意思流行起来"

第2个in与后面the sixties 构成搭配"in the sixties 在六十年代"

(备注：以上2个in各为其主，互补干涉。)

(1)come in(新的观点、时装或产品)流行起来，上市

It was just when geography was really beginning to change and lots of new ideas were coming in.

那时正是地理学真正开始发生改变、许多新观念兴起的时候。

I wouldn't be sorry to see proportional representation and I think it's a thing which will gradually come in. 

我不会为比例代表制的出现而难过，我认为这种制度将逐渐流行起来。

(2)in the sixties在60年代

In the sixties there were the deaths of the two Kennedy brothers and Martin Luther King. 

20 世纪 60 年代，肯尼迪兄弟和马丁·路德·金先后去世。