Geek and nerd had negative connotations when geeks and nerds were commonly poor, but then things shifted and, notably with the rise of the Information Age, being a geek and/or nerd turned into being useful in becoming wealthy. Now it is a compliment.
True of all insults, really. Same reason, for example, words with associations to slavery are considered insults. Or those related to the sale of sexual favours. The implication is that one is poor. Any words you can throw at someone who is rich will be something most people will want to wear as a badge of honour.
Huh? The trickle down line comes from comedian Will Rogers who was making a joke about how President Hoover, who was an engineer, was accustomed to water trickling down, but that he didn't realize money trickles up.
It was a line to serve the exact opposite – to tell the 'proles' that the economic plan was fundamentally flawed.