Why isn't zombie ant fungus more successful?

Zombie ant fungus, primarily Ophiocordyceps unilateralis, is specialized to infect specific ant species, limiting its host range and overall spread. The intricate life cycle and dependency on particular environmental conditions also restrict its success in diverse ecosystems. Additionally, the host ants have evolved behavioral and physiological defenses against such infections, further curtailing the fungus's effectiveness. These factors combined contribute to the limited success of zombie ant fungus in the broader ecological landscape.