The $600 billion reinsurance industry, historically governed by 'old boys' networks' and static actuarial models, is facing a structural paradigm shift as Multi-Agent Reinforcement Learning (MARL) enters the bidding arena. Research reveals that autonomous AI agents are now systematically outperforming human experts by navigating the opaque institutional frictions and 'last-look' privileges that define complex multi-party negotiations. By optimizing for asymmetric information, these agents delivered a 15% surge in underwriting profit while simultaneously slashing catastrophic tail risk by 20%. This evolution effectively renders traditional heuristic-based underwriting a competitive liability for global carriers. As these models maintain resilience even under extreme market shocks, the industry is poised for an 'arms race' where computational supremacy replaces relationship-based deal-making.