Because as much as you dislike them saying layoffs would go all week when they only went through Wednesday or Thursday, you would have really hated it if they said it would only go a few days and it ended up going all week. They were just hedging their bets because it's hard to gauge how long this will take. There were a lot of people that management needed to talk to, either because of a firing or a reassignment.
Again, the real target was always to do most of it on Tuesday. Wednesday and maybe Thursday were just set aside for departments that couldn't get it all done on Tuesday.
People seem to think they have some kind of set schedule to do each day. That's not the case. Each department started Tuesday and got as much done as they could. Some departments got done, some had to spill into Wednesday. I think theoretically some might have spilled into Thursday, but based on how quiet things are here, that doesn't seem like the case.
Finally a down to earth post that explains the method in a realistic manner without all of the speculations. Reposted from @ZcaycF0-fsz