I couldn't agree more with the last point. I'm not saying team chemistry can't be built in one year but it helps to have cohesion, experience playing togethers, and just like enjoy playing each other.And one final thing, Gritty has said some things about this as well, but team chemistry, maturity, and experience with a coach and systems are all intangibles but they do have importance and can cause unforeseen issues. I should perform a statistical analysis on it, but overall, 1st year transfers do tend to be a lot more of a mixed bag than transfers in their 2nd year, even at the same age. Familiarity does seem to have a significant role. That doesn't mean you shouldn't aggressively pursue the portal, but it does suggest balancing that with some development of promising young recruits.
Obviously this past year was extremely talented team but what stood out when just watching mandated press stuff was that they generally seemed to like each other and that energy becomes infectious. Shannon, Coleman, Domask, and Ty really generally seemed to like each other(reason why I think Ty was so emotional at the end of the UConn game) and even guys that had up and down years like Harmon and Goode always seemed bought in. I think that's a big reason why you're seeing guys like DGL and Harris return.
The landscape has changed a bunch but pre-portal when I used to look for sleeper mid major teams that could upset teams and I could watch all season. I would target veteran teams full of guys that played together a bunch. Those types of teams are generally bought in and playing for more than just themselves.