Correct - Butler had quite a bit of success prior to Brad Stevens. They aren't a one coach wonder. Plus, this isn't a school out in the middle of nowhere - Indianapolis is extremely fertile basketball recruiting territory and perennially one of the best college basketball TV markets in the country. Regardless of how Butler performs on the court, they are still an institutional, TV market and geographic fit for the new Big East.
Now, I think SLU makes a ton of sense for Big East expansion since it also meets a lot of TV market and institutional needs. Dayton is a little tougher call - it has a great fan base and they certainly fit as an institution, but their TV market doesn't do much and they don't have much of a national profile. SLU is pretty much a lock for school #11 in the Big East, but the issue is with #12. Everyone else that the Big East is looking at has a major "wart" - Dayton has a small TV market, Richmond has a small fan base, and VCU is a public school.