As was often the case并不是事件频发的意思
as引导的是定语从句 指代后面整句话 即that we had to pack our belongings into boxes and leave out those we had grown to love was often the case.
所以翻译为:我们不得不打包离开伴随我们生长并热爱的人们,这是常有的事
常用还有:
as is known to all 众所周知
as is shown above 正如上面显示的那样