guardian is owned by a trust https://www.theguardian.com/membership/2018/nov/15/support-g...
https://www.theguardian.com/media/2012/feb/23/pcc-guardian-m...
Additionally there has been a culture of rivalry and personal dislike between the Graun (and now Buzzfeed news) staff towards Wikileaks from staff who previously worked with them, namely Janine Gibson and James Ball - it's worth following them and reading their tweets. It would be very naive to think this doesn't affect their (now very negative) Wikileaks & Assange coverage.