The statues in Sen's always bothered me, but thinking about who might have made them and who might have built sens along with the amount of titanite demons there were made me realize something. No where else do we see so many titanite demons, and we know demon titanite is linked to the blacksmith Deity.
What is the statues were going to be an autonomous army built by the blacksmith deity, with a little demon titanite in each of them to breath life into them. Then the blacksmith deity "passed" leaving the army unfinished and scattering the demon titanite into the moat below.