https://signsmag.com/2018/09/fredericks-experiment/

The babies literally died for want of touch

https://vocal.media/history/the-king-who-isolated-infants-to-determine-which-language-adam-and-eve-originally-spoke-i13l0c1o

The emperor’s experiment, however, ended in tragedy. Deprived of emotional and social interaction, the infants did not develop any language and eventually died.

https://www.historyanswers.co.uk/kings-queens/emperor-frankenstein-the-truth-behind-frederick-ii-of-sicilys-sadistic-science-experiments/

Tragically for those involved, Frederick never got an answer to the question he posed, and the original language of mankind remained hidden from him. The children, starved of any form of affection, warmth and basic interaction, died, quite simply, of a lack of love.