Disagree about the SEC's intentions.
They are not competing for eyeballs in regions at this point. They have big enough brands they don't care about getting a 2 instead of a 1 viewer rating in Wyoming.
SEC product strategy is to have the "best" programs and that's enough to drive huge viewership in the handful of prime timeslots. They only need maybe 4 marquee games per week. 16 teams where roughly 8 of them are blue bloods, that's enough right there for the matchups needed.
That's also why FSU has value for them - it's not about gaining eyeballs in Florida. It's about another huge brand to bring into the fold. Clemson is same.
This is a little different than B1G. They are doing same wrt brands, but they ARE looking for geography too. I think the BTN brings value from that, apparently worth the effort. I still wouldn't be shocked if the BTN adds Stanford someday.
But we aren't talking about Wyoming. Does the SEC want to attract viewers in Colorado, Arizona, Utah? And all those schools have sizable alumni bases in California. It would be a natural progression to existing SEC schools in Texas, Arkansas and Oklahoma.
Take it one step further, does the SEC want to encroach on the Big10's Midwest base? Would Kansas and/or Iowa State push the SEC's presence north to compliment Mizzou. If SEC media rights $ remain on par with the Big10, would the SEC make a play for Nebraska? Would Nebraska rather play Oklahoma or Iowa?
You're right, the key for the Big10 and SEC is adding Notre Dame, Florida State, Clemson, UNC, etc. Because for every ++ media rights school, the Big10 and SEC can afford to take a below average media rights school (aka if FSU is worth $125M and ISU is worth $40M, the average/school is $82.5M). And would not be dilutive to the SEC.
The Big10 regional expansion strategy is driven by BTN carriage fees in large MSAs. But what happens if streaming becomes a major player? Amazon, Apple, etc. can broadcast an unlimited # of games and aren't limited to 3 or 4 time slots on Saturday. Streamers might value maximizing people on their platform- not only on Saturday, but the other 6 days a week.