Lanchester's Laws are interesting, and a good starting point, but don't fully address MW:O. It has several assumptions that do not fit well, mostly because it was written at a time when people stood in neat rows and shot at each other.
1. All opponents are armed equally.
2. It disregards 'defensive' armaments like ECM and AMS.
3. It fails to take into account weapon ranges, maneuvers, terrain, and 'winning conditions' other than the annihilation of the enemy.
Most of the 'comeback' victories I have seen fall into 3 categories:
A. One team beats the opponent, but neglected to cap any points, and the surviving light mech waits the timer out.
B. One team is beating the other team, but refuses to respond to a base attack until too late.
C. One team beats the opponent, but the opponents did not go quietly into the night and the remaining mechs (who are usually in decent shape, but missed out on a lot of the fighting for some reason such as defending a distant cap point, or were out of position when the 'big push' came) can take advantage of the opponents shot up mechs.