I see BYU fans happy about their stronger position in the Big12 but I don't see much of your bullet points.

And it makes sense. Utah is a small-time, little brother type with no brand. Their identity is formed around being the anti-BYU.

They thought their inclusion in the PAC was the ultimate BYU diss, so suddenly the enemy (PAC) of their enemy (BYU) is their friend. In this case it got really weird - the PAC was more lover status and all yewts could do was gush about it. And find a BYU fan in whose face they could wag a mocking finger.

This is why PAC12 paraphernalia and billboards superseded and replaced the yewt logo - they didn't really care about their team but they did care about the conference that stuck it to BYU. PAC12 stickers plastered over trucks and minivans, PAC12 billboards declaring PAC12 country (ie BYU not welcome) - in many/most cases without a yewt logo in sight.

But BYU athletics has a brand and no real reason to pay attention to yewts. I'm an exception having lived in Salt Lake County while all the obnoxiousness was shoved in my face, fresh out of grad school at BYU (where nobody cared about the Ewe). Yewts are clearly little brother, with little man disease. You're not going to see Big12 everywhere because hardly any BYU fans care about punching down (hey, I'm not above it after my experience - it's more like punching back for me).

That said, I don't think there's anything wrong with cheering for your future conference mates. You want your conference to have a strong brand because it will soon reflect on our brand. A strong conference makes both wins and losses better than they would be in terms of perception and analytics.