The problem is that the laid fiber can be useful for years while data center hardware degrades and becomes obsolete fast.

It could be a massive e-waste crisis.

Those GPUs don't just die after 2 years though, they will keep getting used since it's very likely their electricity costs will be low enough to still make it worth it. What's very dubious is if their value after 2/3 years will be enough to pay back the initial cost to buy them.

So it's more a crisis of investors wasting their money rather than ewaste.