An easy way is to add an expression on the opacity property to turn off the opacity before the marker.
time < thisComp.marker.key(1).time ? 0 :100;
Or you can select all your layers and run this script to really move layers to the marker position
proj = app.project;
thisComp = proj.activeItem;
thisComp.selectedLayers.map(function(layer){
layer.startTime = thisComp.markerProperty.keyTime(1);
})