Shri Krushna had made many others understand "who is he" -- Shri Narayana himself, supreme Brahman. But after revealing his real identity, he made them forget the revelation by using "Maya", the illusive power.
Reason maybe "the time was yet not right and those people had to yet go through their sufferings (prarabdha)".
Examples being Yashoda, Devaki, Vasudev, Sudama, etc.
For Yashoda, it's mentioned in SB 10.8
But, to some others such as Arjuna, Bheeshma, Kunti, Akroor, Muchukunda, he didn't make them forget the truth. These people always knew the truth.
What might be the reason?