The engine has no idea what you are planning, it is just crunching numbers. Here 2.c6 is not a great choice by black because if you now go 3.d4 what is he to do? The most natural and probably best choice is exd4 and then you go Qxd4. Your queen sits lovely in the centre because black cannot kick it away with Nc6. 3.g3 is quite slow and black can go d5 and be happy with an equal position (his plan with 2.c6). It's good to have an idea of how you want to play the opening but you must be flexible. 3.d4 would give you a nice advantage.
Why did the engine view my G3 move as a mistake?
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I was trying to utilize a Vienna Game Gambit System along with a King's Indian Defense and the said that my G3 pawn move as a mistake. Why would my d4 pawn move be a better move when I'm trying to set up a King Indian defense?