You're right, they hired people that were already participating in the git community to continue to participate in the community. This is better than nothing because it ensures that they are employed, but it's a net zero effect for the git community and isn't what I would call participating because they aren't bringing anything new to the table.
It's similar to Microsoft hiring a bunch of Linux developers to continue developing. Yeah, this is good for marketing checkboxes of 'supporting the open source community', but from the perspective of a developer in that community, it's worthless.
What would be nice is if they hired new developers to work on git so the community actually grows and gets something.