Being who he was?

Hello everybody.

I'm reading How Do You Live by Genzaburo Yoshino.

The conversation they had at that time was a long one, but to be brief,

Uragawa was able to catch up on all his missed schoolwork, thanks to

Copper, and for the moment have some peace of mind. And Copper

being who he was, nothing could have topped his satisfaction at being

able to operate the switch that ran the motor in the tofu shop.

Would you please tell me what the bold part means?

I really appreciate you for the help ??