Why are the ladies not allowed in the Musjid while at the time of Rasulullah (sallallahu alayhi wasallam) ladies were allowed?

Answer

When a person lacks expert knowledge of the Deen, then it is his duty to follow the rulings of the Shariah without voicing any misgivings. 'Why' is a never-ending meandering route which has even distinguished the Imaan of many unfortunate persons. But if you are so interested to have an answer for your 'why', then provide your postal address. Several books answering more than adequate your 'why' shall be forwarded to you, Insha'Allah.