Those standard protection circuits are for other anomalies.  All PSUs have filters and surge protection for AC mains.  An incoming surge on that Monster protector was also outgoing into the attached computer.  Protection inside the PSU was so robust as to make that tiny surge irrelevant.  But that same tiny surge also destroyed even tinier protection inside the Monster.

Protection is always about where hundreds of thousands of joules harmlessly dissipate.  How many joules did the Monster claim to absorb?  Hundreds?  Thousand?  IOW near zero protection.

Protection means no surge is anywhere inside a building.  If anything needs protection, then everything needs protection.  Facilities that cannot have damage properly earth a 'whole house' protector.  A solution proven by over 100 years of science and experience.  And little unknown to a majority only educated by advertising, hearsay, and speculation.

Ethernet cables already have robust protection - typically rated at 2000 volts.  What can overwhelm that protection?  Destructive surges typically occur maybe once every seven years.  And must be connected low impedance (ie 'less than 10 feet') to earth BEFORE entering the building.  Otherwise that current will go hunting for earth destructively via computers - especially on AC - even on ethernet ports.

BTW double conversion UPS often have less protection than power strips.  Anyone can read its specification numbers.  Most do not.  How many joules does that double conversion UPS claim to absorb?  Notice a tiny number.