Because they started that when they felt comfortable and in complete control, truly believing that could control the golem this time. Hubris is one of the flaws literally written into their religion as one of their biggest issues.

Things have been failing for a very short amount time compared to the time they had it under their belt, and they can't just shut off the machine designed to run independently of their direct action.

Its the same reason why they can't stomp out the Palestine supporters despite being a huge thorn for their entire plan.