I don't know if he intended to do it but many coaches are being forced to do it. Spread sets in general and 4 wide in particular does that to you. You simply cannot effectively cover todays, 3, 4 and 5 wide sets with 4 DBs. And obviously putting a 5th DB on the field removes one of the front 7 from the field. Ex-coach Charlie Strong came to UofL with a long resume as 4-3 Under guy, ran it in first year but was nickeling up so much he switched to a 3-3-5 type base scheme.I believe this transition to 3-4 has been intended by Stoops and Eliot from the beginning. Looking back, Stoops has been trying since he arrived to recruit the right personnel for 3-4 defense. Nose tackles, big defensive ends, long outside linebackers, and physical defensive backs. Some notable samples include Melvin Lewis, Matt Elam, Javon Provitt, Alvonte Bell, Kengera Daniel, Kobie Walker, Josh Allen, Chris Westry, Derrick Baity. All ideal for 3-4. The list is long. I am sure others can be pointed out.
Peace