They now have access to private projects so can use that to help create exploits to closed source products that are hosted on GitHub or use it to create their own products or patents.
Look, I hated Microsoft in the '90s and '00s. I was there. I grew up in a world where IBM dominated the market though. They've both changed. The market has changed and both of these companies had to deal with that.
The reality is that nowadays people pay with their privacy instead of with currency for a product; they are the product. Does it matter much who owns the product (independent US company, big player like Amazon, Microsoft, Facebook, Amazon, or Apple?)