How do certain topics and themes stay relevant across time periods, while others do not?

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.