It told the government how to go about building its own data centers. Which meant things like deciding what to build, where, what environmental impacts to consider, etc.
Do we have evidence of what it did? The benefits? The costs? For sunsetting legislation, we should be able to point to something more concrete than vibes being off for datacenters in general.
Not sure what environmental impacts you expect to see the policy to have achieved in three years, but I'm sure we won't truly know the impact until the next future administration that supports environmental science.
I'm not sure you can draw a conclusion like that, especially given that roughly half that time has been under the Trump administration, which really doesn't care about regulations on what it does.
If the policy is about what to do and not to do when building a new datacenter, I could easily believe that the government...didn't actually build any new datacenters during the three years it was in effect, so it hasn't had a chance to have any impact.