Re: Why didn't they push a few more women in NXT before moving them to regular TV?
Because NXT has always had the luxury of only pushing and highlight a few people at a time. During the Horsewomen Era, the scene was basically dominated by them with a few other women sprinkled in. When they left, Bayley stayed behind and then you had Alexa, Carmella, Nia, Asuka, and Emma floating around. After Bayley left and the Draft happened, women like Nikki Cross, The IIconics, Kairi, Ember came up.
And that's left us with the most recent crop of women like Io, Shayna, Candice, Rhea, Mia, Bianca, and Dakota when healthy mixed in with some enhancement talent along the way.
My point is that NXT has always operated like this with rotating talent, though you can argue which crops are better than the others. Now, they rushed NXT to USA because of the threat of AEW, so now they'll have to play catch up.