I looked at several articles on this incident and they never say for sure.
The video mentions they replaced a cable, but that's about it.
If the TV affected wired Internet, that would be very interesting.
Not surprised, if you have anything that is an amplifier you have to work out how to make it not oscillate. A TV has multiple stages of amplifiers and a few oscillators to boot. Not only that but something resonant on a particular frequency will be resonant on interval harmonics thereof. E.g. if something is resonant at 4 mhz it will be resonant at 8mhz, 16mhz, 32 mhz etc. It's not totally rare, here's another goody. Dude had a TV that reached out and touched a rescue satellite. He had a search and rescue crew show up to his house and knock.