They fly low and not in a straight line. Low radar and IR visibility too. IOW you have to be directly in its path to have a chance to shoot it down and because

They fly low and not in a straight line. Low radar and IR visibility too. IOW you have to be directly in its path to have a chance to shoot it down and because of muted IR signature (no jet), your MANPADS will most likely fly right past it even if you are near. But most of these are probably just decoys. The main strike will be timed to arrive when Israeli AD is depleted by them.