1) If we had hired a Junior High coach that had coached 4 undefeated teams in a row, would you still be saying "coaching is coaching?" That is just as ridiculous as saying if you can play the game at NAIA level well, you can play at the D1 Power5 level well..... Just as in the players case, there is a massive difference in the competition level of coaches at each level up the ladder. IF "coaching is coaching" were true, NFL teams would raid HS coaches and pay them 1/100th what they are paying them now. Quality coaches are in fact RARE, that is why they command such huge salaries, and that is why 90% of them flame out at new jobs; they have moved up at least one difficulty level. KG moved up FIVE difficulty levels all at once. She went from coaching against part time coaches to going against seasoned professionals who only coach women's basketball with years of experience at this level. Additionally, every coach but KG out there in WBB D1 came up through the ranks in D1 and has many contacts they can reach out to for assistant coaches, advise, and contacts for players. KG doesn't have that, as painfully shown by the three hires she has made since becoming Purdue's HC. An NAIA coach at an AAU event doesn't get noticed, they are less important to impress than the D1 and D2 coaches and the reps from the scouting services.
2) Recruiting contacts. At NAIA level, coaches have very limited ability to recruit. They cannot travel far, cannot offer scholarships or usually even any guaranteed aid. So a 2 hour drive from Indy was KG's reach and range two years ago, that won't field a Big Ten quality team. I believe her recruiting budget was $200, for gas for her to drive places at Marian.
3) Outside of Purdue fans, Katie Gearlds is barely known or remembered. She is far less relevant or remembered than Joseph, Douglas, White, or even Figgs. She was a good but not great college player who's teams perennially underachieved and accomplished nothing of note during her 4 years here. Additionally many of those that remember KG as a player remember her as the laziest defender for 3 years to ever wear a Purdue uniform, not something that brings you great credibility as a coach. Purdue has had 9 first team All Americans, Katie Gearlds is not one of them, she was third team and her jersey got hung up because of a powerful booster making it a contingent of a big donation and other political motivations, not that she earned it on the floor.