This is interesting: That the “highest form of WISDOM” is kindness takes me to understandings of the nervous system, cognition, and relationships...in addition to the virtue of kindness itself.
A nervous system that gives and receives kindness is likely in a more relaxed state; thus, it's not going to respond from a fight/fight/freeze/fawn response. When the body is at ease, more intentional/skillful/wise decisions are accessible and utilized.
Cognitively-kind thoughts (seeing the humanity in self/others) will likely lead to better questions from several perspectives to consider what wisdom might say to a given challenge.
Lastly, relationally: Kindness is an attitude of mind and heart that is expressed in our actions and felt and received by the giver and receiver of kindness. We tend not to forget a kindness and whether we've given or received it, it brings us closer to ourselves and others.
To aspirations of wisdom, enacted and cultivated through acts of kindness!