What features of the Amiga chipset architecture and/or Amiga OS made it possible to design the Video Toaster run on the Amiga?
Why weren't there similar (cost-effective) video products for the PC or Mac?
I think is a mix of features that made the videotoaster a good match for the Amiga.
The big thing is that the Amiga can natively work in NTSC. Don't know about early macs but for example VGA is totally incompatible with this standard so PCs weren't used that much for video editing in those days.