as for the corruption: again i have to ask.... WHY? how would they have gotten here if even the Will has trouble accessing bet? this suggests the Will sent corruption over but that begs the question of *why*? it seems counter to the Wills stated goals for Taylor if the Will sent corruption over to mess with taylor, and atleast this time the Will stated they wish to save the world not kill it so letting corruption run loose seems counter to that goal
It's hard to tell what the Will is ever planning. In the first chapter, it states that it's currently more pissed off with the Entities than with Humanity. Humanity is everywhere on the Imaginary Tree, it deals with us all the time. Getting forcibly shut out of a particular branch offends it though, so blood must be spilled.
If we take that at face value, then everything it does on Earth-Bet, from Taylor to Lisa to Dinah, goes towards goal of eliminating the Entities. How these acts help it, we don't know, but they probably
are helping somehow.
The idea that was stuck in Dinah's head was "saving the world from Abyss Flower", and while somewhat hostile, it's open ended. It could be meant to line up certain parahumans for Taylor to knock down. The Will may consider the removal of Entities to be incomplete if parahumans are still around, so why not arrange for them to challenge Taylor?
As for how the Will is doing these things…
What we know, is that Thinkers who focus their powers(Shards) on Taylor, and get
particularly unlucky, get the Will's attention. This contact is presumably how it's done things like implant Lisa with the Gem of Serenity, and connect Dinah to Corruption(?). It normally can't interfere, but if Shards try to touch the Will, it touches back. Aggressively. It apparently only had enough leeway to awaken a single Herrscher, which it used up on Taylor, but the more channels it creates, the better the chance of a Gem it implants Awakening. It might just be taking chances whenever they come up, given how rare they are, and it makes these plans on the spot based on the circumstances.
…arranging native opposition to Taylor could also be a long-term plot to encourage be her to cut loose with the Honkai energy, saturating Earth-Bet much faster than what QA is doing. The more fights she's in, and the harder they are, the more energy she channels.