Content syndication VS guest posting for link building

I was going to start reaching out to do some guest posting on tech sites for a white hat website I own but I thought I'd just check why people generally seem to choose this route over content syndication.

Do bloggers never want to publish content that is already indexed elsewhere even if their readers will enjoy it?

Or does the content never get indexed so the backlinks don't either?

Has anyone had a successful link building campaign with content syndication?