everything we do in poker is a probability, rarely do we get all the money in with a 100% chance to win, anda t times we get it all in as an underdog.
Thus, bankroll management covers the mathemeatical probability that we will lose as a favourite several times in a row, because at some point its bound to happen.
I could theoretically sit at 12 1knl tables with my bankroll, forgetting for a moment im probabl a break even player at those stakes at the minute, the variance caused by the aggressiveness of those games will make me go busto in no time.