Erasmus has moulded a squad of which most Test nations are jealous, boasting an unmatched strength in depth from one to 15.
Coming into the Wales game, the Boks had beaten Scotland (32-15) and England (29-20).
The seven tries to two victory over the Welsh meant the Boks finished the year with 11 wins from 13 Tests and go into 2025 as World Rugby's number one ranked team.
Their sole losses were one-point defeats by Argentina and Ireland.
"It's more important how all those players slotted in and how we didn't really lose a lot of momentum, which probably I thought would have been the case," Erasmus said.
"With a new attack and defence coach, chopping and changing, I think we definitely did lose the rhythm of that game at times.
"But for Siya (Kolisi) and all the other guys who were captains this year, how they pulled the team and stayed together, it's really important."
Erasmus said at the start of the season, his concern had been how the players would "accept that we're not 25 players but 50-plus".
"I didn't know if the senior guys would understand they would probably make their careers longer if they don't play every single Test match every week and give the younger guys a chance.
"We actually said, 'Those who don't want to buy into this, unfortunately you can't be part of the group'.
"Those results mean a lot."
South Africa racked up 57 tries in their 13 Tests, something Kolisi credited former All Black Tony Brown with being instrumental in.
"He's been really big," Kolisi said.
"The nice thing for us is every four years there's always something new.
"It's not the same gameplan all the time. The coach wants to build squad depth, so when someone's injured we don't panic.
"Our motivation doesn't come from outside, it's from what we’re capable of doing."
Kolisi added: "I'm really happy with how we've ended the year.
"Without the other leaders on the field, honestly we wouldn't be here. I'm really proud of what we've achieved as a team.
"It's really a special group of players and really a special environment that every guy that comes in doesn't want to leave.
"So we're enjoying it as much as we can while learning and growing at the same time."
Despite condemning Wales to a record 12th consecutive Test defeat, Erasmus insisted that the game had "not been a walk in the park".
"They're such a gutsy team," said Erasmus, part of the Springbok team that lost 29-19 to Wales -- for the first time in history -- in the opening match of the then-Millennium Stadium in 1999.
"I don't know what there is to get right behind the scenes but Warren (Gatland) is a great coach.
"They always hanged in there, but for a team with 14 caps average against a team with an average of 45, there are some solid guys in there."
