Apple design their own Arm-compatible cores from scratch. Ampere use a modified Arm Neoverse N1 core. In addition, the Ampere server that Marcin is using is about 6 years old, and would have been tuned for core count over single thread performance (good for web serving). Basically Arm's own cores aren't nearly as good as Apple's at the best of times, and having a 6 year old server makes things even worse.