It's an inherently different thing. Fibre is infrastructure. It'll still function decades later. GPUs at this scale are consumables. I've heard 3-5 years lifespan before they fail out. This might be a low estimate, but even if you double it - they're 50% of the cost of datacenters. We're flushing entire countries worth of economic value down an Nvidia shaped toilet.
It's not that they fail (which they also do), it's that they become obsolete. They consume more energy to do fewer operations relative to newer nodes. This is the basis behind Moore's law.
So 10% failure rate per gpu year. Some might be repairable and there might be a failure rate acceleration as time passes etc. So very approximate numbers.