There is no one right answer here, but there is a clear background for early recruiting. Actually, it is not all that recent. It was started by John Savage when he was hired at UC Irvine about 2-3 years before they fielded a team. Rather than go strictly JC's to build a team, he used those 2-3 years to do early recruiting of players (largely in Southern CA and especially in Orange Cy) who would come to Irvine as freshman when they had their stadium built and would start play in the Big West. The model was successful for Irvine. That model was successfully followed by Coach Horton and Oregon when they started their baseball program shortly after Irvine.
I would expect another factor in early recruiting was the contract signed at Tennessee about 5-6 years ago by Coach Serrano. At that point, his contract at $600,000 per year raised eyebrows and expectations.
Many of those who posted on this board at that point pondered the impact of the coaching salaries escalating, the elevation of the CWS profile on ESPN, and the general fact of more $$$$ in college baseball in terms of how those might change the "business side" of college baseball.
Looked at over time, I do think there is the one fact alone which lead to the start of early recruiting and that aspect falls squarely with Coach Savage and Coach Horton and their being successful with the approach with entirely new programs.
Once a model was in place which showed it could work, however, college coaching salaries increased both recruiting dollars and financial "pressures" to get the best players. Combine those dynamics with the proliferation of PG and the long time limitation of regional recruiting was no longer in play.
Finally, with the further proliferation of travel ball and PG and showcasing, even down to 14-15 year olds, we find a perfect recipe for college coaches to get verbals from the top players at the earliest stages with the least allocation of recruiting dollars. PG often posts here about how the best players they see at 15 are still the best at 18-19. While the recipe is not perfect, the early "verbal" gives the college coach all the protection he might need while the player and parent will always feel the downside would "never happen to me."
In my view, college coaches and their AD's are fully incentivized. I doubt this changes much, if at all, going forward. Using this approach and a CWS title, Coach Savage now has a contract through about 2025 at around $1M per year at UCLA. The flip side with Coach Serrano shows life isn't a bowl of cherries for the coaching staff who does not win. He has made over $2,000,000 in the last few years. However, it does not seem likely anything close to that income stream will be in his future.