Why did the pilot in this EC135 crash change the throttle setting after encountering wake turbulence?
It's the second sentence on the first page of the report:

He inadvertently rolled the throttles to manual, and never restabilized the
engines or main rotor rpm.

Supplemented by (the next sentence):

In addition, he did not understand the reset procedures for the
engine controls (FADEC), and never returned the engines to FADEC control.