Did you watch Sampson? As Jimbo notes, he was Charmin soft, got pushed all over the place, was woefully inefficient for a guy his size (.516 true shooting in the regular season, .487 in that finals) and an absolute turnover machine (3.6 per 36 minutes that season).
At age 25, he was off "one of the most promising starts to a basketball career in history" in the roughly same way 32 y.o. John Lucas was "promising" and a key part of that team despite not playing. Lolz.
"Sucked" is relative, but Sampson being their #2 guy is not really a compelling case that that team was not shitty by the standards of NBA finalists.
Sampson came to the NBA in an era where the vast, vast majority of players played an entire college career. Today, the best players MAYBE play two seasons, and most just one, in college, before turning pro. So we have to evaluate Sampson's NBA career in that light, not in modern light.
His first two seasons, he put up these numbers:
1983-84: 21.0 points, 11.1 rebounds, 2.4 blocks, .523 fg%
1984-85: 22.1 points, 10.4 rebounds, 2.0 blocks, .502 fg%
Yes he was supposed to be a legendary player, and those numbers aren't "legendary". But that's a pretty damned good start to a pro career.
For comparison's sake, here are a few other centers and their first two seasons....
Ewing:
1985-86: 20.0 points, 9.0 rebounds, 2.1 blocks, .474 fg%
1986-87: 21.5 points, 8.8 rebounds, 2.3 blocks, .503 fg%
Olajuwon:
1984-85: 20.6 points, 11.9 rebounds, 2.7 blocks, .538 fg%
1985-86: 23.5 points, 11.5 rebounds, 3.4 blocks, .526 fg%
Robinson:
1989-90: 24.3 points, 12.0 rebounds, 3.9 blocks, .531 fg%
1990-91: 25.6 points, 13.0 rebounds, 3.9 blocks, .552 fg%
Shaq:
1992-93: 23.4 points, 13.9 rebounds, 3.5 blocks, .562 fg%
1993-94: 29.3 points, 13.2 rebounds, 2.9 blocks, .599 fg%
Daugherty:
1986-87: 15.7 points, 8.1 rebounds, 0.8 blocks, .538 fg%
1987-88: 18.7 points, 8.4 rebounds, 0.7 blocks, .510 fg%
Mourning:
1992-93: 21.0 points, 10.3 rebounds, 3.5 blocks, .511 fg%
1993-94: 21.5 points, 10.2 rebounds, 3.1 blocks, .505 fg%
Mutombo:
1991-92: 16.6 points, 12.3 rebounds, 3.0 blocks, .493 fg%
1992-93: 13.8 points, 13.0 rebounds, 3.5 blocks, .510 fg%
Duncan:
1997-98: 21.1 points, 11.9 rebounds, 2.5 blocks, .549 fg%
1998-99: 21.7 points, 11.4 rebounds, 2.5 blocks, .495 fg%
Sampson's numbers were really good his first two years, pretty much in the same breath as most of these other guys who all went on to have really really good NBA careers. Some guys on this list are among the best players of all time.
I forgot how sick Robinson and Shaq's numbers were, right out of the gate.