自生自灭成何事
Subject of this sentence:
云
自生自灭 run its course
自 in and of itself
生 be born; grow
灭 extinguish, vanish, die
成事
成 accomplish
事 thing
See also:
成事不足,败事有余。
⋯⋯能成大事。
成大事者,⋯⋯
谋事在人,成事在天。
成何事
何 what
自生自灭成何事,能⋯⋯无。
-->
自生自灭成何事?能⋯⋯无?
Running its course, (the cloud) accomplish(es) what thing? (It) can ... ?
Why the cloud has to accomplish something (for the people)?
Bucause here, as a metaphor, it refers to those who have authority, power, etc.