Like passing ships

[Vladv1]

"Like passing ships, just as the overweight and drug-damaged T. Rex star seemed on an inexorable decline, so AC/DC’s comet appeared to be burning ever brighter".
Mick Wall, "Hell Ain't A Bad Place To Be".
To me "like passing ships" seems out of place here", is it a part of an idiom? What does this part mean here?

 

[Skrej]

It's a paraphrased version of an idiom, yes.

https://dictionary.cambridge.org/us/dictionary/english/like-ships-that-pass-in-the-night