Either that router is still just as fast as when it was new. Or it does nothing - at minimum, a port blown out. Routers will run just as fast 20 years later.
You protector was so grossly undersized as to explode on a transient too tiny to harm anything else. First, remember how electricity works. If a surge was incoming to that protector, then at the exact same time, a similar current was also outgoing into the router. That same current simultaneously was also in the sky and also connected to and in earth. That current was simultaneous in every part of a multikilometer path.
So a current too tiny to overwhelm protection inside the router also exploded that protector. Of course. Read its numbers. How many joules did it claim to absorb? Appliances will often convert hundreds of joules surges into rock solid and stable low voltage DC to power its semiconductors. That same current exploded a near zero protector.
Second, take a $3 power strip. Add some ten cent protector parts. Then sell it for $25. Profits are extreme. Protection is near zero. But just enough above zero to hype it as 100% protection to consumers who beg to be scammed; who ignore spec numbers.
Any facility that cannot have damage would never waste so much money on protectors - let alone a near zero one. Effective protection means hundreds of thousands of joules dissipate harmlessly outside. Then no surge current is inside hunting for earth ground via appliances. Then even near zero (plug-in) protectors are protected.
More relevant numbers. Lightning is typically 20,000 amps. So a minimal ''whole house' protector is 50,000 amps. Because any protectors that fails catastrophically was doing absolutely no protection. And was enriching its manufacturer.
Learn from your mistakes. Fix the problem. What is protecting your dishwasher, air conditioner, smoke detectors, clocks, refrigerator, CFL and LED bulbs, etc? Nothing. If anything needs protection, then everything needs that protection. Protection is always about where hundreds of thousands of joules are harmlessly absorbed. Protection means nobody knew a surge existed because even protectors must never fail - become the source of fires.
A surge too tiny to overwhelm protection in all household appliances (TV, router, dimmer switches) also easly destroyed a near zero scam. Did you learn from the experience by first learning relevant numbers? Or just assume the router must be getting slower - without even one number to justify that believe?
Your protector exploded because it did exactly what manufacturer spec numbers said it would do - near zero protection. A protector is only as effective as its earth ground - which plug-in protectors do not have and will not discuss. Otherwise an obscene profit margin would be at risk.
