Why did God create us? I believe it is because He wants us to spend eternity with Him in Heaven. It is as simple as that.
Our life on this earth is only a temporary journey in preparation for an eternity with our Maker and Creator in Heaven; together with His Son Jesus and the Saints and Holy Spirit. By Saints I mean all those loved ones who have gone before us in a state of grace and love for God.
God wants us all in Heaven for ever. The invitation is sent to everyone. But not everyone responds. Some indeed turn down the invitation and decide to go their own way believing what they want. Denying the very existence of God even.
And God allows them to go their own way. No one goes to Heaven against their will. No one is forced there.
Just like any loving parent hurts when their child goes astray; so does God grieve when we choose our way as opposed to His. He grieves bitterly but allows it to happen.
It is fashionable these days to proclaim that God does not exist. It is all folklore and antiquated thinking and belief.
Years ago I worked in London, close to Saint Paul's Cathedral. No one at work knew I was a Christian. Talking about religion and politics was not encouraged at work. One day I visited St Paul's Cathedral with a colleague. As we entered the vast building he waved his hand in the air in grandiose fashion and said, "Tell me Vic, do you believe in all that?" Meaning God and Christianity.
I replied, "Yes, as a matter of fact, I do!" He said nothing. But from that day he acted differently towards me. More polite and respectful. So did other colleagues. In time, other senior managers also acted differently towards me a junior. Word had got round about me. Maybe they thought I was odd, weird, whatever ... but at least they saw me as different.