How does Ibn Taymiyyah authenticate the accounts of those who killed Husayn and those who condoned his killing, if he curses them? And does the curse mean that they are hypocrites and infidels, and their narrations are not accepted?

Indeed, Al-Husayn was killed unjustly as a martyr, and his killers were numerous transgressors.

May the curse of Allah, the angels, and all people be upon whoever killed Al-Husayn, or aided in his killing, or was pleased with it. The narration of Al-Husayn's killer is unacceptable because he is not trustworthy, and trustworthiness is a condition for accepting a narration. The Imams have explicitly stated that the narration of Al-Husayn's killer should be rejected.