When we are limiting economics to merely explaining everything we mean it has limited  application in using  to control our affairs and direct  economic behaviour towards the individual good or collective welfare. What we mean is that it is a mere post facto thing and not a tool for guiding the economic affairs of the community or the individual. This of course is a controversial thing to say .But the real question is whether economics explains everything. when we say economics can explain everything we say that humans collectively behave in particular ways which lend themselves to being read as patterns .I really do not know if large thought movements in a market which is globalised can be spotted and economice decisions taken on the basis of such knowledge. However the herd mentality can perhaps be mapped by a close understanding of the market but surely over short spans of time and not across years or decades.