This was the moment many former Sun people identify as the 'death of original Sun'.
Sun wanted to make SMP work, so Solaris was a huge amount of work and was incredibly buggy for a long time. Sun effectively lost a huge amount of time going threw this transition and it took years to be back to the same amount of stability. Bryan Cantril talkes about this in LISA11 - Fork Yeah! The Rise and Development of illumos [1]
But not everybody agree, if you read 'Sunburst: The Ascent of Sun Microsystems' that was written in 1991, they are very pro the AT&T deal and explicitly call out the BSD people as 'anti-Standard' and thus anti-Sun.
The real difference there is the argument about what a Standard is. Their approach is basically Unix belongs to AT&T and therefore they are the standard. While the (in my opinion) more correct argument was that BSD/Sun had the most software and they were the defacto standard and being more open, continuing be the standard was what Sun should have done.
Another incredibly important battle was over X vs NeWS. NeWS was arguably technically superior. There is a nice talk by James Gosling about it [2]. It still had technical problems but it would have been a great base to build off. But because some companies, lead by Dec made X open(ish) and many embraced it, X became 'the standard' and thus many at Sun basically said 'Well X is the standard, so therefore we have to switch to X'. Instead of saying, lets make NeWS open and try to be the Standard.
The Sun transition also hurt their costumers. In "LIFE UNDER THE SUN: My 20-Year Journey at Sun Microsystems" David Yen mentions costumers bitterly complaining about it. They made the transition very, very aggressively basically telling costumers to STFU. David Yen loved the aggressive approach because he was selling massive SMP servers that need Solaris. SMP servers where clearly where Sun saw the future.
If Sun had embraced BSD, open sourced NeWS and made the SMP transition in the open, Unix might have gone into the 90s being an unstable juggernaut.
Sun wanted to make SMP work, so Solaris was a huge amount of work and was incredibly buggy for a long time. Sun effectively lost a huge amount of time going threw this transition and it took years to be back to the same amount of stability. Bryan Cantril talkes about this in LISA11 - Fork Yeah! The Rise and Development of illumos [1]
But not everybody agree, if you read 'Sunburst: The Ascent of Sun Microsystems' that was written in 1991, they are very pro the AT&T deal and explicitly call out the BSD people as 'anti-Standard' and thus anti-Sun.
The real difference there is the argument about what a Standard is. Their approach is basically Unix belongs to AT&T and therefore they are the standard. While the (in my opinion) more correct argument was that BSD/Sun had the most software and they were the defacto standard and being more open, continuing be the standard was what Sun should have done.
Another incredibly important battle was over X vs NeWS. NeWS was arguably technically superior. There is a nice talk by James Gosling about it [2]. It still had technical problems but it would have been a great base to build off. But because some companies, lead by Dec made X open(ish) and many embraced it, X became 'the standard' and thus many at Sun basically said 'Well X is the standard, so therefore we have to switch to X'. Instead of saying, lets make NeWS open and try to be the Standard.
The Sun transition also hurt their costumers. In "LIFE UNDER THE SUN: My 20-Year Journey at Sun Microsystems" David Yen mentions costumers bitterly complaining about it. They made the transition very, very aggressively basically telling costumers to STFU. David Yen loved the aggressive approach because he was selling massive SMP servers that need Solaris. SMP servers where clearly where Sun saw the future.
If Sun had embraced BSD, open sourced NeWS and made the SMP transition in the open, Unix might have gone into the 90s being an unstable juggernaut.
[1] https://www.youtube.com/watch?v=-zRN7XLCRhc
[2] https://www.youtube.com/watch?v=4zG0uecYSMA