As you're preparing to upload 1,000+ products using the Shopify CSV Import feature, you find out that Shopify is creating one product only and trying to create variants of all the other products within that specific product.
Since your variants don't have any variants, you mapped Option1 to "Title" and Option1Value to "Default Title".
So why is this not working? The reason is quite simple, always keep an eye on your handle column.
The handle serves as the main index point for the Shopify import process, if you keep it blank the import won't succeed and cause all sorts of issues.
What does your handle column contain? If this is the same for all products it will consider them all as variants of the same product handle. If none of your products have variants then just copy the content of your product title column into your handle column.
That should do the trick!