For the record: Knowsley Safari Park held a lot more African elephants than the ones remembered (in most briefs). Popularly known are male Krueger (transferred to Port Lympne in October 2006), and females Buta, Shaba, Juba, Tana, Ashanti and Nala. Between 2004-2007 4 births occured with only Ashanti and Nala surviving calves.
This does exclude some cows present when the Windsor Safari Park transfer deal came through in 1993. Females Masai (from Windsor and deceased November 1994 at Knowsley), Kora (also from Windsor SP and deceased May 2005 in Knowsley), plus several other cows pre-imported in 1971: Choto and deceased September 2004 at Knowsley, Adega and deceased June 2004 and Rosemary and deceased May 1994 at Knowsley.
Still later on they received sub-adult/adult male Nissim in November 1998, who was intended to become the intended breeding bull of the future. He died unfortunately in June 2014 at Knowsley (having collapsed).
TBH: the biggest mistake IMO was sending off bull Krueger in a herd that had just started breeding and would have done so had he not been permanently moved off exhibit in 2006. Now, it would have taken probably another few years to create some good matriarchal lineages and that would probably have secured African elephant ex situ captive-breeding for years onward. Now bull Krueger sired thrice calves while at Port Lympne, but has no living offspring.
In July and November 2017 females Juba and Ashanti and Tana with Nala were moved to Zooparc de Beauval. Alas, female Nala died unexpectedly while on transit to Zooparc de Beauval same day.
IN CONCLUSION: with some plusses and minusses added here and there your judgement cannot hold up against the available evidence. Agreed that if and had ... bull Krueger remained at Knowsley and be allowed to breed to all the cows at the Safari Park, I remain convinced female Buta would have bred, birthed and reared her calves successfully, likewise females Tana and Shaba and quite quite possibly later on females Nala and Ashanti. With a proven bull leaving and an inexperienced (and quite much younger than the adult cows bull like Nissim would not stand a chance in the dominance stakes). Now, this of course all in hindsight, but still a bit different than what you might have expected.