A cynical person would say that this is because the stated targets weren't actually the targets, just like with this act. (Stated targets: sex traffickers, real targets: tech companies offering e2e encryption)
Yes, IMO FOSTA/SESTA were deliberately malicious and yet another successful attempt to force puritanical ideals upon our citizens, regardless of the damage it would cause.
The senators who initiated the bill are not dumb. They knew exactly how it would play out.
There was plenty of warning of the effects of these bills on sex workers. Legislators at best ignored them, and at worst were happy for these side effects, depending on where they sit of the political spectrum.