This doesn't seem like a valid/useful comparison, at least not in terms of financial consequences.

Goldman Sachs is estimating that hyperscalers alone will spend around $5T on AI expansion between 2025 and 2030. Compare this to the $200B total spent on 5G by the big carriers. The 5G bill is about 4% of the AI one.

5G was a one-and-done investment to upgrade the carrier's networks, and while they are now all saddled with masses of debt, it is not crippling to them. The carrier's level of borrowing never depended on revenue growing exponentially, and limited debt to what they could reasonably service.

In contrast AI infra investment isn't just a one-and-done "let's update our datacenters from H100's to Vera Rubin", but rather a very aggressive bet on the size of the market growing - more datacenters, not just datacenter upgrades - in a market where no-one has any real idea what the demand curve (both for the product itself, and for FLOPs) is going to look like.

It reminds me a bit, as an ex-Acorner (UK 1980's) of Acorn almost self-destructing by wrongly estimating YOY growth in the newly emergent computer market, and being left with warehouses full of rapidly depreciating computers as a result.

As with Acorn, the directional bet of AI eventually needing a lot more compute than today seems pretty secure, but guessing the actual rate of growth in a brand new market is highly error prone. It's a bit like the difference between investing in stocks vs options. With stocks you only need to get direction right. With options you need to get timing right as well.