So is the post-facto realization of "we knew masks work, we just didn't want the people to grab all the supply".
* N95 masks
* Everything else
We knew N95 masks worked because that's what professionals use in hospitals. Unfortunately, there was a shortage of PPE so telling people to buy them would put them in direct competition with professionals treating very sick patients. In April 2020 we were looking at a really bleak scenario so there was a very strong incentive to keep professionals alive even if it came at the expense of some citizens (think: doomsday scenario).
We also had no idea whether 'everything else' helped at all. Recommending non-N95 use might have given people a false sense of security that might have played against more effective measures such as extreme social distancing and self-quarantining of people with symptoms.
As knowledge improved, guidance changed. Nothing crazy to see here.
Recommending people use masks could've given people a false sense of security in people and probably acted against more effective measures such as social distancing and self-quarantining of people with symptoms matching those of Covid-19 ('well, I know I have a cough, but I'll just wear a mask and it'll be fine').
Recommending people use the only masks we knew to somewhat work - N95s - would've created a huge problem for hospitals that already were having issues procuring PPE to protect the professionals who were dealing with Covid-19 patients.
Basically, there was no reason for the CDC to recommend masks. Again, there's no need for some nefarious explanation.