Because in native speech, the object tends to come at the end of the clause. This sentence uses the past autonomous, and is roughly translated to "One birthed him in Dublin".
Léigh sé é cheanna versus Léigh sé cheanna é. I'd argue the latter would be more common for a native speaker. The more recent placement of the object directly after the subject is likely due to the influence of English.
I'm curious about her pronunciation of "rugadh" here, which sounds sort of like "rugu" (or "roo-goo".) I thought that kind of /u/ at the end was more of an Ulster thing and that the speaker's accent wasn't Ulster. One speaker at forvo says something like "ru-gak" and the other "ru-ga". Just curious. https://forvo.com/word/rugadh/#ga
adh isn't always "oo" in Connacht - as far as I know the "oo" sound is used for the saorbhriathar when it ends in -adh in the past tense.