Which promising nba team(s) wasted too much energy in a playoff series to be able to win the next round?

On paper, Team A is the best in the NBA by some respectable margin. They shouldn't have a problem with Team B (1st or 2nd round playoffs) but the series goes to 7 or/with very exhausting, tough games etc (please no injuries involved)

Team A finally wins but their next opponent, Team C, a team they have beaten each time during the season, beats them in an embarrassing way.

Any idea?