Are referred candidates more likely to get hired?

I think it really depends on culture to culture. Where I am from (and a lot of parts in MENA) - referral (or sometimes called 'wasta') is a really good way to land a role.

And companies also even prefer hiring someone who is through a known source since job boards/hiring tools are still not that 'as common' as the west.

HR and Recruiters are still owning all new hiring, and hence, knowing one or two, can be the way you get your next gig.