While I'd lean towards the Olympus, the first question would be, do you currently have Nikon DSLR gear?

If you currently have some Nikon lenses, if you get the Z50, you could always purchase the Z mount adapter to use your current glass on the new Nikon.

Otherwise, definitely the Olympus system, fantastic weight (or lack thereof) and good quality.

With your budget, perhaps;

Olympus E-M10 MkIII
Olympus M.Zuiko 14-150
Olympus M.Zuiko 75-300 (AF is a little on the slower side in dull light, but shouldn't be too much of a problem on Safari)

Looking around $1,900 for everything, leaving enough to get a spare battery