SOMEONE (the federal government through congressional appropriations) has to pay for it (through contracts). It can take a couple months to get a contract done (the right way - i.e., putting it out for bid, reviewing the contract proposals, getting clarifications on the responses, etc).
Remember the fiscal year was over September 30 and they had to get some kind of CR in place (which we are still under) and then get the debt ceiling fiasco taken care of (which it finally was... for now) and while all of this was going on, comb through the funding from the last COVID appropriations to see which line items they would use and how they would apply the funding for kits. Then of course was deciding which kits - will they all be one brand or several that can be selected? And on and on.
I expect this had already been in the pipeline and once they were ready to finalize the whats and wherefores, they "announced it". It also required the creation of a website and database to do the kit requests ("orders" ), so that was probably another huge contract and I know they don't want a repeat of healthcare.gov but I expect there will be anyway - that's unfortunately how rolling out huge brand new data systems end up - bugs galore and overwhelmed servers (virtual cloud instances).
Just a lot of logistics that have to go on behind the scenes and I can imagine the whole thing is going to probably crash on day one. I hope hope hope I am wrong but there has been so much pent up demand that it will be like trying to score tickets to some hot concert.