Answer:
Most immigrants had experienced so much extreme change and uprooting, they felt like they had witnessed enough change to last several lifetimes.
Some topics are general and are regarded as 'classical' because they are always relevant across time periods through being relatable even as time progresses. For example, topics or themes about politics and satire would still prevail until now. Other topics or themes (such as viral videos) are only for that particular event and do not always occur, thus they do not prevail in the long run.
first one is (MAIN CLAUSE)
second one is (SUBORDINATING CLAUSE)
but i am not sure about the 3rd one
