what would be the point of keeping it in it's new form, cleansed if their was no one to live on it?
Who said no one is to live on the Earth? Why must ONLY the great crowd be the ones to live on Earth? You are assuming that this WT teaching has to be correct or otherwise it would not fit with other WT teachings.
If you choose to believe the bible and want to be a Christian, there are a million different explanations out there as to what happens to the Earth long term. It's up to you what you want to believe, the bible is not clear on the matter.
The more you learn about the bible itself, the more you'll see it's not very clear really about anything, and thus why many don't consider it to be divine at all.