* He knew the curse was powerful and could spread. Cutting off his hand would not eliminate the curse, and there was a risk that it could spread through his body.
* He wanted to use the curse to his advantage. Dumbledore knew that the curse was linked to Voldemort's Horcrux. He wanted to use the curse to weaken Voldemort and eventually destroy the Horcrux.
* He was aware of the risks. Dumbledore was a powerful wizard, but he knew that the curse could be fatal. He was willing to take the risk because he believed that it was necessary to defeat Voldemort.
Ultimately, Dumbledore's decision was a calculated risk. He knew that there were dangers involved, but he believed that the benefits outweighed the risks.
It's important to note that cutting off the hand wouldn't have been a simple solution. The curse was complex and deeply embedded in his body, and it's likely that even if he had severed his hand, the curse would have still affected him somehow.