Board Thread:Questions and Answers/@comment-30953250-20190821085026/@comment-34962159-20190821093355

Basically, Accelerator wasn't in optimal condition at the time, due to Last Order's illness and Misaka Worst's injury (the latter caused by him), so he wouldn't make the best decisions. Another reason is action anime logic: normal humans (or characters with the physical capabilities of normal humans) are capable of fighting superhumans simply because it looks cool.