In the Fifties, I think there's at least two years where Topps wasn't setting out to issue a final series of cards before pulling the trigger: 1952 and 1958, with 1957 and 1959 also being possibilities.
We all know the story in 1952 (and I expect some player contracts with competitors that expired in June also had a hand) but in 1958, with baseball expanding and until Topps had Musial in the bag, I don't think that last series was necessarily a foregone conclusion when the set was originally designed, although I suspect that by the time the fourth series was being prepped Topps had enough market info to allow them to proceed. Excluding the AS cards, the player mix is just awful, full of unknowns and rookies, with a couple has-beens thrown in. There's some other reasons too, I think. Some more on that at my blog:
https://www.thetoppsarchives.com/201...ing-slots.html
1957 is strange one, with that tough semi-high series and 1959 could mirror the prior year but for 1952 and 1958 it sure seems like some extra thought went into the calculations.