You can conspiracy theory this as much as you'd like, but honestly, the simplest answer is that it just isn't that simple.
"Shipments coming through commercial carriers, which represent about 95 percent of de minimis parcels, will need to have informal or formal entry designation documents and pay the relevant tariff.
Shipments coming from international mail carriers have the option of choosing an ad valorem tax rate, which is the effective tariff rate imposed under the emergency economic powers law used by Trump to deliver his initial “reciprocal” tariffs. The tax is then based on the value of that package.
International mail shippers can also notify CBP that they are choosing a “specific duty” for their package ranging from $80 per item to $200 per item. That option is only available for six months whereupon shippers will need to use the topline ad valorem tariff rate."
Source:
https://thehill.com/business/5476144-de-minimis-exception-to-be-lifted-friday-what-to-know/
I work in software. I don't think I could reliably get something in place that's been thoroughly coded, tested, cyber hardened, and deployed to handle such an increase in volume. And that's not even accounting for all the new documentation that needs to be spun up, staffing that needs to be increased, training of new staff, and so on. The EO was signed last month. It's an extremely short period of time for a precedence that has been in place for over a decade.