Earlier quoted context omitted.
The very short is, that AT&T between 1974 and 1982, due to the telephony monopoly rulings, wasn't allowed to sell software. Thus they gave their research results to universities, like Berkely.
How different is that from tech giants using their monopoly profits to develop software that they give away for free? You say AT&T gave away some software to universities. Similarly Google gives away Go (among many other projects) as FOSS for anyone to use. If Google didn't have to worry about money, they might not develop these things to give away for free.
They give away Chrome for spreading it and giving them control over web standards.
AT&T gives UNIX away as they have no revenue stream on top of it and it being research.
Google isn't giving out their research work.