No this is misinformation that continues to be spread.
The Iberian blackout was caused by a lack of reactive power leading to voltages going out of their designed ranges.
The Iberian grid had adequate inertia at the time.
Reasonable grids have forced inverter based generation to manage reactive power for over a decade. But Spain due to lackluster processes relied on thermal plants to provide it. And they didn’t provide the expected amount.
There were some more confounders around oscillations and what not but the central cause came down to voltage control. Which is near trivial to solve in 2026. If you just force everyone to do it.
I'll look into this further. I heard about this from a podcast episode on The Great Simplification, I'd be very surprised if it turned out to be misinformation though its always possible. Nate is pretty damn thorough in his research and sits squarely on the left half of the political spectrum, I'd usually expect misinformation like this to come from the (US) right.
Here's the final report on the blackout from ENTSO-E:
https://www.entsoe.eu/publications/blackout/28-april-2025-ib...
From the summary on the page:
> The investigation concludes that the blackout resulted from a combination of many interacting factors, including oscillations, gaps in voltage and reactive power control, differences in voltage regulation practices, rapid output reductions and generator disconnections in Spain, and uneven stabilisation capabilities. These factors led to fast increases of voltage and cascading generation disconnections in Spain, resulting in the blackout in continental Spain and Portugal.
It even models scenarios where they double and triple the available inertia to see if it would have had any effect:
> The above analyses indicate that, even under the assumption of perfect execution of defence plan actions, neither these measures nor additional inertia would have been sufficient to prevent system collapse.
Here's the US regulation from 2016:
> As a result, all newly interconnecting non-synchronous generators will be required to provide reactive power
https://www.ferc.gov/sites/default/files/2020-06/RM16-1-000....