So, the malevolence needs not only GK at relics, but also JKA and his ship, in addition to either fives or ahsoka at least at g12. Then you also need a tank, either HT at relics, or BTL-Y-Wing. all of thoose arent on the way to SLKR.
Whereas you are getting the geos allready, and the other 2 ships for the malevolence are pilotless (Vulture Droid and Hyena Bomber). Thus you only need to put some gear into GG (and he rly aint that bad to get him to g11, and when you relic him later, he makes for a scary squad, even with leftover garbage droids). Thus that fleet is alot cheaper to build for you, than going for the negotiator. (Also the Geos do work fine at g12 for that fleet, for a long time, whereas negotiator without at least relic JKA, relic GK and either 7* BTL or relic HT is gonna struggle)
Only relicing the capital is sadly not enough for the Negotiator, whereas malevolence is a bit more lenient about that. it can do very well with only GG on relic levels.