Umbridge attached great importance to the intelligence "extracted" from Harry and Ron, conveying the news back to the Ministry of Magic at the first opportunity and winning Fudge's high praise.
Snuffing out danger directly in the cradle was obviously quite a difficult task.
Yet the Ministry could hardly send elite Aurors to fight head-on against Acromantulas, especially in a godforsaken place like the Forbidden Forest. That flock of giant spiders was even more dangerous than Dark wizards, and even elite Aurors could easily lose their lives there if they weren't careful.
Chapter 1020