He didn't become rich and powerful by blowing his money on gaudy ships.![]()
Plenty of rich people spend money on gaudy things and they still are among the wealthiest people in the world. What is the point of money if you never spend it? Rich people often seek superior status over others, by buying opulent things. The Ferengi hoarding money like Scourge McDuck makes them seem silly, it makes the comparison between them and modern capitalists less plausible.
Also Zek did get kidnapped in "The Emperor's New Cloak" so clearly security was an issue. Heck, from what have seen in various Star Trek shows, Federation starships seemed to be attacked by random aliens all the time, it would make sense that most of the same dangers apply to a Ferengi starship. In Realm of fear, I believe it was mentioned that a Cardassian warship was attacking Ferengi ships.
Now regarding the Ferengi's supposed neutrality, this attitude seems to be contradicted by TNG episodes like "Peak Performance" where a Ferengi starship decided to pick a fight with the Enterprise for no real reason.