You are right to notice that Chinese pop songs have an unusual propensity towards depth and form in its lyrics when compared to English pop songs, though I’d argue that it’s not always the case.

To my observation, language indeed has a lot to do with its occurrence. For this answer, I’ll assume you refer to the Mandarin dialect. For one, many common idioms in Mandarin (成语) consist of only four syllables. There are easily thousands of idioms collected and recorded throughout the ages, with some idioms dating back to a thousand years, many of which are commonly taught in Mandarin language classes. The average Mandarin speaker would know at least 50 common idioms, many of which carry deep meanings and a historical context to consider. And the best part? All that in just four syllables.

On top of that, the Mandarin dialect (as well as other Chinese dialects for that matter) is a very flexible form of language. I’m not a linguist, so I can’t tell you the technical specifics, but the rough explanation is that the grammar for Mandarin is not quite as stringent as say English. This gives songwriters the option to place certain words in unique and unusual orders, and still have it sound correct in the ear of the listener. This helps with rhyming and rhythm.

Finally, because Mandarin is a logographic language, a single character (one syllable) can be packed with meaning. So in some ways, Mandarin can be very efficient in conveying thoughts and ideas with far less syllables when compared to English.

These are observations so far. I hope it helps.