The 146 was originally conceived by deHavilland long before BAe. Back in 1966 I was told that if the Harrier did not get ordered then I could expect to go to Hatfield and deal with it. It was designed as a hub and spoke aeroplane to open up Africa where there were no facilities at the end of the spoke. Literally none.
Because they did not want it stuck at the end of a spoke with an engine problem they decided it had to have four engines and be certificated to RTB without pax on three.
Since some strips were expected to be pretty rough the high wing was chosen to keep the intakes as far from the surface as possible.
Eventually BAe happened and decided to launch the design on the back of super quiet for parts of the US and the rest as they say is history.