More likely it was the 1979 supreme court case Reiter v. Sonotone Corp which instituted the "consumer welfare standard" which shifted antitrust enforcement from focusing on protecting competition in markets to "protecting consumers" which made it much easier for large mergers to be approved.
Don't SPACs generally move the needle in the opposite direction? ie they turn private companies into public ones.
An existing public company merges with a private company to make that private company public.
The SPAC is created for the purpose of that transaction though. If SPACs weren't a thing the private company would exist and the public company would not.