Why are these Iron Masters helping him?

No Master could help these two.

When my Master helped King Amber keep his throne, I mean.

I said, "So now all men are happy, having the Masters to rule and help them, and there are no more wars and wickedness."

(She later learns that the Master has been helping her in this.)

The Master of Ceremonies then helps the celebrant find his place in the Missal.

Master and journeyman helped the man to a chair, and then Sebell poured him wine.

Masters helped Patrick to his feet and supported him to an adjacent office.

I'm sure your Master will help you.

But truthfully, unless they did worse, I wasn't going to turn them in if the Master of the City could help us solve the mutilation murders.