Understanding behavioral drivers of success in illicit digital marketplaces is critical for developing effective enforcement strategies and understanding digital commerce evolution, as darknet drug markets represent a growing share of the total drug economy. This study employs quantitative regression analysis of 50,000+ listings from 2,653 vendors in the Agora marketplace (2014-2015), examining relationships between cybersecurity signaling (PGP encryption mentions), product diversification, and commercial success through nested regression specifications controlling for reputation, pricing, and category-specific factors. Product diversification emerges as the dominant predictor of vendor scale, increasing the odds of large vendor status by 169% per additional category, while PGP encryption signaling functions primarily as a professional marker rather than an independent success factor. Vendor success depends on portfolio breadth rather than specialization, with category-specific enforcement creating differential market constraints. Successful vendors operate as diversified enterprises capable of rapid pivoting between product categories, requiring targeted enforcement towards diversified vendors based on coordinated multi-category enforcement approaches rather than traditional substance-specific targeting strategies.