pass by

[mengta]

But sometimes when firm-specific aspects are unimportant, outsiders who dominate insiders by a significant margin are passed by to promote an internal candidate.

I can't figure out what the sentence mean.
"outsiders are passed by to promote an internal candidate" what does that mean???

[twostep]

The insider got the promotion.

[mengta]

could you please explain it in detail?

[twostep]

I do not quite understand your question? The insider got the job, the outsider was "passed by" - did not get it. To pass by - not be included.