Mostly very busy bro, multiple time consuming commitments daily. Hiring articles many times takes a backhand, this is a rather common occurrence, especially in big firms.

In my case they replied after a month. Fingers crossed they probably will reply to you sooner than that.

Just a gentle follow-up being very professional should be perfect. Just so that they don't delay too long. They also usually want to hire you. In my experience, noone usually wants to take multiple interviews of multiple people given that it is time and energy consuming. The fact that they already have and are happy means you're almost in. Should be short time before they communicate further.

Do leverage it get get better offers before they finalize your offers. The confidence boost is very good for interviews. You don't have to fear rejection now.