Why was the LORD angry with Eliphaz and his two friends?

Answer: They had not spoken rightly of Him

God said His wrath burned against them because they had not spoken about Him accurately, as His servant Job had.

“After the LORD had spoken these words to Job, He said to Eliphaz the Temanite, “My wrath is kindled against you and your two friends. For you have not spoken about Me accurately, as My servant Job has.”— Job 42:7 (BSB)