Surge electrical current will take a lowest impedance (not low resistance) path to earth.  That path starts in a cloud (three miles up) and connects to earthborne charges (maybe four miles distant).   If that path remains outside, then all appliances are protected.

To keep that current outside, a connection from an incoming path (ie AC electric wire) must be as low impedance as possible to earth.  But that impedance can never be low enough.

50 meter separation means a higher impedance between protector and appliance.  Higher impedance created by separation means another and lower impedance connection to earth is a better path.  IOW protection increases due to higher impedance when a path from incoming AC electric wire and properly earthed protector has many times lower impedance on a less than 10 foot connection to earth.

Protection is always about this conductivity. When a best connection to those charges (four miles away) is a low impedance connection to earth, then almost no current need fight through high impedance on a 50 meter wire.  Then that current need not be inside.

That is conductivity.  Another relevant factor is equipotential.  Equipotential is why only one earth ground (single point earth ground) must exist.  Since we cannot make sufficient conductivity, then improve equipotential.  Since we cannot make sufficient equipotential, then better conductivity is required.

Best protection for cable TV is a hardwire connecting low impedance from cable to earth ground.  No protector is required.  Telephone wires cannot connect directly to earth.  So your telco installs a 'whole house' protector, for free.  That protector is only doing what the hardwire does better.  Effective protector does not do protection.  Effective protector is a connecting device to what does protection - earth ground.  A protector is only as effective as its earth ground.

What sometimes makes it so difficult to grasp are the many erroneous concepts that promote plug-in protectors.  Those are sold as if a protector does protection.  The concept is difficult to unlearn.  Protection is not about the box.  The box is only a connecting device.  Protection is something not sold in stores - earth ground.  Unlearning what advertising promotes can be hard.