Why did they poison Laika?

Could you elaborate on the controversial decision to poison Laika, the first dog sent into space? It remains a haunting aspect of the Soviet space program. Why did they opt for such a tragic fate for this brave canine? Was it a necessary sacrifice for the advancement of space exploration, or was there a lack of consideration for the welfare of the animal? The circumstances surrounding Laika's mission continue to spark debate and questions regarding the ethics of animal testing in space exploration. What were the motivations behind this decision, and what can we learn from it today?