Why connected node count have dropped since august 1st?
A common cause for a node's connection count going down and staying down for a while is IP address changes: It can take a while for knowledge of the new address to percolate in the network.

Otherwise, your prior high count could just have easily been caused by an attack or spy-peers that have since stopped.

It's a bit hard to say since the expected number of peers of a listening node depends on how many other peers are in the same /16.