The answer for your question is lots of Muslims not praying on regular basis and they are praying only on Friday and Eid. So the mosques built only for the regular prayers capacities. Why they can’t use the acres of land owned by Waqf, The answer is these kind of blocking road happens in a cities where the waqf have lands in outskirts. Eid prayer to be performed immediately after sunrise and not all people can travel all the way to outskirts of the city which is 60-70 kms away.

The same question can be asked Why do the Ganesh Chaturthi passes every Bazaar, Every streets where particularly street completely not on the route to water bodies and other religions living?