Earlier, when the strange bird had first called out, Di Tou had already gained an inkling of what was going on, but in the heat of the moment and in the midst of the fight had not had a chance to properly mull it over and devise a countermeasure.
Although there were perhaps geniuses out there with high battle IQs who could instantly devise strategies and create plots while fighting, he wasn't one of them, and even if he was, he was far too inexperienced. It was only in the long run, and after carefully spending time thinking in the small gaps between attacks, that he could carefully consider the problem and solution.