Transfer Portal
Looking at examples like Trinidad Chambliss at Ole Miss - went from a DII Power Ferris State to the SEC and is now in the Final Four.
Incarnate Word QB Cam Ward - went to Washington State for 2 years then made Miami a contender overnight, then was the #1 Overall Draft Pick.
Both of these guys spent multiple seasons at other programs before joining the 'Big Time'. So the examples are there, I just don't see a ton of success year 1 after leaving FCS or any lower level of competition.
Also, to some extent you can talk about QB Shadeur Sanders as well -- though I think SS could've landed at most D1 programs if he didn't follow his Dad to Jackson State...then eventually to Colorado.