At least, one hopes that their trading strategy is based on a combination of financial fundamentals and a technological speed boost; if the speed boost is the only thing they've got going for them then that doesn't speak very well of their business.
I agree that in the financial use-case, the trade-offs are different, and perhaps you can just turn off your wireless link and just fall back to normal fiber when it's raining.
To address your last point, under my limited understanding of high-frequency trading, the edge is in predicting small fluctuations in price, and acting first. For that kind of trading if you incur unpredictable latency, you'd expect to lose money on more trades, since your orders come in after the latency arbitrage has been removed.
You still need to be able to (somewhat) accurately predict those price movements, but that prediction is meaningless if you can't also execute quickly. So the speed boost is a necessary but not sufficient criteria for executing many HFT strategies.