Why does the European MALE RPAS UAV use twin engines?

Question

I don't know why the European MALE RPS UAV designers chose to use twin engines?

I know two engines are expensive but add safety...

Does choice is to obtain mass flow @ Medium altitude(low air density)?
especially with relatively low speed(maybe 0.4~0.6 Mach)...

I guess that as density drops off at higher altitudes, the machine ingests less air mass, resulting in reduced power and reduced thrust...

To need larger flow areas (larger diameter)?

Unlike RQ UAV series...

Answer 1

According to the Airbus press release:

The MALE RPAS is the first unmanned aerial system designed for flight in non-segregated airspace and will be capable of performing a range of missions in intelligence, surveillance and reconnaissance, both wide area and in theatre. A twin-turboprop propulsion system will deliver energy for the mission system and provide proper redundancy to limit restrictions when operating over European densely populated ground and unrestricted airspaces.

Essentially, the aircraft is intended to be operated in the same airspace as existing air traffic, over large urban areas. The twin engine configuration is to provide redundancy and thus stop a robot plane from crashing on people.

Answer 2

Three months after you've asked the question, the Wikipedia article you provided a link to in your question was updated to state:

The drone's dual engines were a demand of Germany, which intended to use to UAV for surveillance over domestic urban areas and was concerned that an engine failure in a single-engine drone could lead to the drone crushing a house. [sic]

Wikipedia states this article as the source for the German demand for redundancy.