It IS hard to imagine that a student-ATHLETE would turn down an offer to attend a top-notch school that happens to compete in a "power" conference in order to attend another top-notch school which happens to play in a minor conference (Ivy). Obviously, Llewellyn must have his reasons to do so but it is hard to imagine which are those reasons (academics is NOT one of them, since Stanford is at least every bit as good as Princeton academically). Presumably he not only values education (which either school would fulfill) but also the sport he plays....and there isn't any doubt that athletically the PAC-12 is VERY far above the Ivy league.
Since others have already addressed the facile side note, let's discuss the primary assertion. Over the last two completed recruiting seasons (2016/17), for instance:
Chris Lewis, 4-star PF, 68th in nation per ESPN, picked Harvard over offers from Alabama, Auburn, Arkansas, Cal, Georgia, Georgia Tech, Kansas State, Memphis, Miami (FL), Mississippi State, New Mexico, Notre Dame, Tennessee and Texas A&M.
Robert Baker, Jr., 4-star PF, 97th in nation, picked Harvard over offers from Auburn, Butler, Clemson, Georgia, Georgia Tech, Miami (FL), Texas A&M, USC and Vanderbilt.
Seth Towns, 4-star SF, 98th in nation and a Columbus native, picked Harvard over offers from Ohio State and Michigan.
Bryce Aiken, 4-star PG, 99th in nation, picked Harvard over offers from Auburn, Creighton, Illinois, Miami (FL), Oklahoma, Rutgers and Seton Hall.
Sebastian Much, 3-star PF, picked Princeton over offers from Arizona State, Utah and Washington State.
Jordan Bruner, 3-star SG, picked Yale over offers from Clemson, Georgia, Tennessee and Temple.
Jarrod Simmons, 3-star SF, picked Penn over offers from BC, Georgia Tech, Pitt, Providence, Temple, Texas and VCU.
A.J. Brodeur, 3-star SF, picked Penn over offers from BC and Notre Dame. 247 reports we had interest but didn't offer. He was one of Aaron Falzon's prep teammates.
Jaron Faulds, 3-star PF, picked Columbia over an offer from DePaul.
Plenty of power conference offers around the Ivy's most recent slews of recruits, including some offers from stronger academic schools as well. Harvard leads the way, but even some of the second-tier basketball programs have culled some good talent over high-major offers.