Those Siege towers are incredibly powerful. They buff each other, and make taking cities extremely easy. On the downside, you still need to clear out enemy units before you roll in those towers.
Assyria is very good at catching up in tech through war and to me it made a lot of sense to beeline the Siege Tower and then get the rest of the tech tree by conquest! Once you start rolling with Assyria, a domination victory is pretty straightforward. The problem with that strategy is you do somewhat neglect early infrastructure. If you come up against an opponent first who has a big military and can take your towers down you'll be in a lot of trouble.