Question

why vision was so weak in Infinity war?... ​

Answer 1

Answer:

AS HIS SAPPHIRE WAS TAKEN BY HIS GIRLFRIEND!!

Answer 2

$\huge{\tt{ ANSWER }}}$

He was stabbed with a blade from behind that made him weaker. Corvus Glaive's staff disrupts his ability to function and his atoms were not be able to fully restore. That's why he was not able to fight back.