Why did our acharyas not travel to South India when foreigners became oppressive?

After Lord’s departure, we heard preaching was sidelined because of foreigners rule. Then why did not Achryas tried to spread in favourable places like South India, where there was no foreign influence. We never hear that our acharyas went allover India and debated with different religions to propagate Gaudiya Vaishnavism (Like Ramanujacharya,madhwacharya etc., did).