You're going to be building a lot of towns and a lot of them are going to get destroyed. In fact I would say ideally most of what you build is going to eventually get destroyed. (hopefully not before you can compensate appropriately of course)
In order to get points you want to allow as much controlled destruction as possible, by that I mean you want them to kill as many of of each others units and as many of each others buildings as you can while keeping at a level where they can still rebuild, expand, and produce units fast enough that it won't wipe each other out.
Making defenseless towns is part of that, but you don't always want your towns to be completely defenseless. You'll want to make sure that they aren't being destroyed so fast that it outpaces construction and you want to make sure you can compensate for lost resources.
You'll also want towns to be able to put out enough units and have enough defenses to allow you to use mythological and god tokens without tipping the balance too much, and some of those are worth points when used. Putting down mythological and god tokens before your towns and units can compensate for them is a common way to lose games early.
The stronger your towns and units are, the more abuse your setup can tolerate from mythological and god tokens without tipping over, and being able to use those is another major source of points.