I'll give you some back story;
7 was born in an economically challenged third world country on the brink of a large-scale starvation, but was given the chance to go to a first-world country to show how aid was needed, he was stick-thin and you'd only ever notice his head, although the french ironically noticed his arms too.
9 was a sloth, but ironically quite a healthy sloth yet still with a plump body, he didn't care to even glance at 7 in his pristine but deafeningly isolated lifestyle, because he was stuck in his own self-depreciative ways. Even when a salivating 7 came to meet him, he didn't even bat an eye-lid and told him to go back home as he dosed senselessly.
7, being such an under-nourished individual thought now is the chance to get my feed in this kingdom, but having spent the day travelling and becoming overwhelmingly disoriented, he lept upon 9, capturing him and gnarling away at his body.
That is why 7 8 9.