The difference is definitely not known to be due to current environments' relative abundance. Maybe you got that from the Wiki article on bonobos which include

The difference is definitely not known to be due to current environments' relative abundance. Maybe you got that from the Wiki article on bonobos which includes a deceptive quote of a 2014 Nature article. What the article actually says is that bonobos have a genetic adaptation due to historic evolution in environments with abundance which either allows for phenotypic variation in response to current environment, or which has resulted in biological evolution to less violence as a general policy (which would indeed be "nature"). Personally I'm strongly inclined towards the latter hypothesis because it's the most parsimonious and fits observation better, ie the number of observed bonobo murders is near zero despite varying environments. If we find modern bonobos living in some scarcity who take up murder as a result, then I'll change my mind. Chimps on the other hand are believed to be violent because it confers genetic fitness (as per that same Nature article), and things such as the age and sex of their victims is predictive suggesting they murder in order to eliminate competition. This is their nature in the sense that this behavior is significantly impacted by their genes.