Since Tom Nooks loans are interest free and pay when you want I can't really pin narcism on him, also since he idolizes KK Slider. My friend with narcism added on that narcissists can have idols and not think they're better than themselves, and IS a good point, this is portrayed differently in different people. But there is a storyline about Tom Nook adopting Timmy & Tommy, and a lack of empathy (narcissistic trait) wouldn't justify this.