@Cue7 Because I don’t think the administration is bothered about the issues that bother you. Their priorities are different from yours and many others on this forum.
Here is what I speculate happened
The administration decided that it was time to play the ED game because it is more advantageous to the school and attracts more affluent students (Chicago sorely needs that demographic to make up for the many decades of lack luster endowment growth). ED kids who choose Chicago as their first choice will also be happier and probably have a better feeling towards the school. However the administration did not know how strong or how deep the potential ED pool was, so they decided to play it safe with an ED2 option, in case the ED1 number was quite low.
Surprisingly they got a decent number of kids applying ED1 and then ED2. If they reject or wait list too many to make room for the EA/RD pool, then they would be sending the message that “ED is not a big advantage at Chicago”, which is exactly the opposite message they want to send. They would also be making room for kids who are either price shopping or not as enthusiastic about the school. These kids may never show up at Chicago or may cost Chicago a lot of financial aid money. So they admit kids they feel would be a good fit and have good stats in the two ED pools. That number is quite large because the pool is strong.
Even with the lower number of apps in the deferred EA/RD pool, they now don’t have too much room for the RD/deferred EA crowd. They cut back quite a bit but they still need to admit enough so as not to make that pool totally irrelevant going forward. At this point, they are probably hoping for a lower yield in this pool, but unfortunately for them, too many kids accept and so they have a larger class size than they anticipated.
I think in coming years Chicago will probably settle in at around 55% of the class in the ED/ED2 pool, but this being the first year, they wanted to send a strong message that applying ED to Chicago matters.
Having introduced ED1/ED2, it makes absolutely no sense to “admit conservatively”. That would be a terrible idea for the school, even if it would be great for the EA/RD pool applicants.
We can argue about whether Chicago should have joined the ED bandwagon, but once they did, given their ranking and recent surge in popularity, the probability of what just happened was pretty high.
It will take them a few years to tweak the admit rates in each pool, but I suspect they will eventually look more like their peers.