Simple, but accurate. Guys who make a beeline for the best, don't play diva with the terms/location/judges/etc and get the dangerous fights made regardless of what it takes. Getting prissy about purse cuts when you're the underdog is how to avoid getting to a belt in the first place... But it's irrelevant once you're there - at that point, showing true self confidence is all in who you choose to fight.
It's why Benavidez accepted a 5m low ball from team Canelo, and he never heard from them again. Something OP strangely forgot to mention..
However you want to describe the way Joe Louis carried himself - that was confidence! One specific example was Joe getting married just hours prior to his fight against Max Baer, leaving Joe with a marriage yet to consummated. Max merely presented as a **** blocker who Joe got out of there ASAP so he could get down to “other, more important business”.