It's all about money is what it's all about. Adding Stanford and SMU and Cal may have helped the ACC bosses but it did not help FSU, UNC or Clemson in any way. Weaker teams ?? One could argue it was actually hurtful to their programs.
The biggest thing it did was basically give FSU and Clemson a bigger slice of pie temporarily.
Their ESPN deal has a pro-rata as new (qualified) teams are added, so every new team nets the conference another $20 Million or so. Stanford and Cal are only taking about $6-$7 million per year from the ESPN media deal for the next 7 years, then stair stepping to 100% in 10 years (right before the grant of rights expires). SMU is taking $0 for I think the next 9 years. That other $50-$60 million is going to be split among the other members.
Their brand was already hurting, so I'm not sure Cal and Stanford made it worse (SMU maybe), but now they have conference games on the other coast which is going to be a headache logistically. I'm not sure they had another real option to add anything significant money-wise without selling naming rights, etc. If they did, they likely would have exercised it.