We still don't know how to make a time machine, but as long as we have the one we've got, we're fine.
Maybe you think we're immoral, but it works, and why not do it, there are an infinite number of universes out there, so why not take advantage?
We never made a time machine, but we thought that as long as we committed to inventing and making one, raising funding and setting a project plan to get it done, then the possibility that we were the timeline that invented the machine was about 50%, and thus if we were lucky, we could opt out of finishing the project.
We were lucky, the second day of the project, our future selves arrived on an initial test run. It was thrilling for us, but not for our future selves as it suddenly dawned on them that were were going to be initiating our intended plan B.
After killing the time travelers, we figured out how to operate the machine and began using it to provide us with all sorts of goods (going back in time and stealing from the same place we just came from). The hardest part was always getting energy back. We wanted gigawatts of power, but could only really bring back batteries. Kinda wished we'd spent the extra time figuring out how to build a time machine ourselves, we could have made it bigger.