It’s a legitimate question to ask:
Why did God give us the Great Commission, if He can do it all on His own?
Based on the whole core concept of our Christian faith, I would guess it has to do with being in a relationship with God.
It might be similar to that day when I let my two year old daughter help me set up a piece of new furniture. She was so eager to help with the pliers, even if it wasn’t a required tool. Although I could’ve made it all on my own and would’ve been even quicker that way, it was obviously quality time I spent with her. Because of that, we most probably grew closer together.
In Revelation two, Jesus rebukes a church for doing all the right things without being intimately connected with God in the whole process.
“I know your deeds and your toil and perseverance, and that you cannot tolerate evil men, and you put to the test those who call themselves apostles, and they are not, and you found them to be false; and you have perseverance and have endured for My name’s sake, and have not grown weary.
But I have this against you, that you have left your first love.” Rev 2:2-4 (NASB)
We need to repent and stop doing things for God without Him. Nothing we do will come to fruition, if we fail to abide in God on a consistent basis (Joh 15:5). And since God does all the heavy lifting anyways, we can relax more and spend more time at His feet rather than running around like a headless chicken thinking our work has some kind of value at all… (Luk 10:38-42).