So a mix of their own motivation and likely support of Israel, being told, of being paid, and being pressured by backlash if they report contrary opinions, or as you said, tell us lies.
But by whom then? Who's behind this? Israel? Pro -Israel thinktanks? Someone else? All of them? Sorry, please don't take this in a bad way, but I find it hard to believe that you don't care enough to never have thought about it.
Edit: added something
Ah, hier ist die Lügenpresse-Fraktion wieder am Start. Schön! Lass uns raten: Glaubt den Medien nicht, irgendwas mit Schafen, etwas etwas DiE jUdEn kontrollieren alles, iNfOrMiERt eUcH, irgendwelche obskuren Internetseiten ...