A bull market is merely a rising market. You can get a bull market because the economy is thriving, but you can also get a bull market because speculation is rampant. The former is a good thing. The latter will end with a crash. Optimism is characterized as a good thing, but over-optimism is a fool's paradise and speculation is greed trying to get something for nothing. When the economy is working, people are creating things of value. In a speculative bubble nothing of value is being created.
Thus the bull is an ambiguous symbol. Stock traders love a bull market regardless of its roots, and the really savvy ones will make money on the rise and will make even more money in the collapse when ordinary folks get wiped out and lose their homes and their livelihoods.
Pop culture today loves girls who kick butt, and the smaller and slighter they are, the more we love them. Scarlett Johansson or Kate Beckinsale running roughshod over the bad guys. Nobody is going to cast a female Russian weightlifter in the role of kick-butt heroine. But Lucy Liu will always be popular in that role. Or Chloe Moritz as Hit Girl in Kickass. Thus we have Fearless Girl where 50 years ago it would have been a working-class man. The bull artist may not like it, but his bull means very different things to stockbrokers and the working poor. And Buffy telling the monster "I'm not afraid of you" appeals to a lot of folks these days. It may look like the bull is going to trample her, but Fearless Girl, in today's culture, has a surprise waiting for him.