Angel hardly had any investment in this trade at all, from start to finish. The White Light Bullets were transformed from undead, which belonged to Black Castle, and so did the Infant Spirits.
Of course, it wasn't fair to say there was no investment whatsoever.
Without his concoction of Samsara Overture, none of these subsequent events would have been possible.
Angel continued to move forward, and not long after, the second and third White Light Bullets were successively loaded into the magazine.
Having been caught by surprise once by undead suddenly burrowing up from the ground, Angel this time also included the underground in his surveillance area to prevent a recurrence of the previous situation.
But sometimes, crises don't necessarily come from unchecked corners—they might also stem from negligence.
The surrounding wizards were basically just stopping the undead conglomerates, while other souls were allowed to approach Angel, for Angel to deal with using Samsara Overture.