referb mmm fried

I run a 60 3300kv madussa in a slayer.
I just put in the mmm the other day and using a 5000 30c 3s pack and ran for the duration of the pack well. Felt the components and everything was barely warm. I go to put a second pack of the same kind on and nothing happens, so thinking its dead pack I try another pack that is freshly charged just to see if it powers on(2s pack). It lights up for a second then poof the smoke comes and you know how the rest goes.

I know my gearing was good.
I know my connectors were good.
I know I had a free moving drivetrain.
Still have the two speed set up so that would help if anything on lowering the amp load.
I run and set up the mmm for mechanical brakes.

I would like to know what I did wrong or what I can do?