Realization dawned upon Vaan as he could guess what had attracted the Death Eaters' aggression.
After all, Hecate would have known where he went or at least had a general idea of it. Thus, if he suddenly disappeared due to the Garden of Thyia's powerful restrictions, it would prompt her to investigate his whereabouts.
However, his arrival did not draw the attention of the Death Eaters. So, why would it happen to other visitors?
Thanks to his earlier conversation with the Elder Spirit, Vaan gained a lot of valuable information and could speculate likely reasons for the Death Eaters' sudden movements.
For example, the Death Eaters weren't just guardians of Goddess Thyia's inheritance but also the protectors of the Garden of Thyia itself.
After all, the Wood Spirits were vulnerable beings due to their nature.