#1 Assistant,
I'll go back to your original post and try to answer, at least from my perspective.
My oldest transferred from a D1 at the beginning of Spring 2017. Never in our wildest dreams did we envision a transfer when he committed to his D1 initially. He committed as a SS, but played immediately as a weekend starting pitcher.
There's a zillion reasons why kids transfer. His issue wasn't playing time. Lots of off the field issues and immaturity. Great school. Loved the coaching staff. Academics were awesome. And my then 18 year old behaved like he was 12. Who knew it would work out that way?
NCAA rules govern how transfers work...Rick at Informed Athlete was crucial for my son to navigate the steps. Getting permission to speak to other schools from his D1 was one of many steps.
My son, working with my wife and I, developed an academically and athletically vetted list of schools just like we did when he was in high school. All were 4 year colleges. None of the schools had seen him play in college or in Summer leagues. A few had been on his initial list in high school and remembered him. He reached out to coaches with his college and Summer stats, current video, etc., and he reached out to Admission reps with his college transcript. His list was only about a dozen colleges. Schools had to fit with his desired major that was already in process, realistic opportunity to immediately compete for playing time, weather, facilities, etc. Many of the same things that factored into his original decision making plus some things (e.g., short time to complete his degree) that were different as a transfer student.
My guy had two remaining years of eligibility. That probably helped more than having only one year left. That said, it really was about mutual fit. If the college has a need and the transfer player can fill that need, then even one year of remaining eligibility could work. Of course the converse is four years of remaining eligibility doesn't mean much if the school doesn't want you or you get on campus and don't perform.
He transferred in to the school in January and immediately was a weekend starter. A couple other guys transferred in the prior Fall and didn't see the field. A kid needs to show up and perform in the classroom and compete on the ball field, just like the first time around.