Thats too much underestimating for one team.
Do not forget they are still NBA players and even in their weakest season they could still win a game. I am niether a fan of Lakers nor Lebron James but I just know any team could win even those in highest rank. That was proven by Grizzlies before winning the 1st round against the number 1 seed San Antonio.
You just dont when they will have a good game and on the Lakers side, they are still creating their chemistry.
I agree that this is too much underestimation. NBA is where truly amazing happens. Even though an underdog could beat someone that is bigger than them. Just remember when LeBron isn't a Laker yet, they have the same kind of W - L last season. And that was just a show from the youngcore.