Chamberlain played at a time where the average player was worse than they were in Shaq's day, so Chamberlain would be double/tripled teamed on every single play and he would still drive home baskets at an unstoppable rate.
He was taller and had a wider wingspan than Shaq, stronger than Shaq, more athletic, had better conditioning and would play entire games, he could actually shoot the ball too.
https://www.youtube.com/watch?v=8O9MgNfcGJA
Even a retired Chamberlain has a larger frame than Shaq did as a young man.
https://www.youtube.com/watch?v=bU43dTuMuig
This was a player who was absolutely dominant unlike any player in the league. Shaq was never that player, he was dominant for his position. Chamberlain had seasons where he was the top scorer, top rebounder, most minutes played and top 10 in assists while leading his team to the championship winning MVP and first all team honours and all-defensive first team honours.