This is a bit off the mark.

Cats have only been domesticated for like ~10k years, so not much in the way of change or adaptation has happened. So wildcats have the same capacity for forming social bands and such, they just don't in the wild as they don't have any incentive to.

Neoteny is easy to achieve in 10k years. Cf. the Soviet experiments on domesticating foxes, which started showing juvenile, gregarious traits in a few generations of selective breeding. In general felids are social in kittenhood within their family unit, most wild species just "grow out of it" in puberty. Selection pressure (natural or artificial) favoring individuals that tolerate or even enjoy human (or conspecifics') presence favors retention of juvenile traits in adulthood, and this change can happen quite quickly.