One major difference between 2012 and 2016 is the non Romney and non Trump candidates never had such a commanding lead over the rest of the pack like DeSantis does over the non Trump field today.
Look:
https://www.realclearpolitics.com/epolls/2012/president/us/republican_presidential_nomination-1452.html#!
It is literally one after the other of non-Romney candidates rising to commanding leads over the rest of the pack to challenge Romney, and then collapsing.
First Perry rises to a commanding lead in comparison to everyone else other than Romney. Then people see Perry exposed to the scrutiny of a front runner in a debate, and Perry collapses shortly thereafter.
Next Cain rises to a commanding lead in comparison to everyone else other than Romney. Then people see Cain exposed to the scrutiny of a front runner in a debate, and Cain collapses shortly thereafter.
Next Gingrich rises to a commanding lead in comparison to everyone else other than Romney. Then people see Gingrich exposed to the scrutiny of a front runner (don't remember if it was really a debate that did the coup de grace), and Gingrich collapses.
Next Gingrich rises to a commanding lead in comparison to everyone else other than Romney. Then people see Gingrich exposed to the scrutiny of a front runner (don't remember if it was really a debate that did the coup de grace), and Gingrich collapses.
In 2016, you had the same sort of dynamic with other candidates rising up to challenge Trump, leaving the other ones in the dust for a week or two, and then collapsing, the main difference being that they could not rise as high as the one-hit-wonders of 2012 because Trump was consolidating too quickly.
Also DeSantis unlike the others is not a flash in the pan candidate and has been building his narrative for years at this point .
So had Rick Perry, Gingrich, Scott Walker, etc. They didn't just appear from out of nowhere and suddenly run for President.
At the end of the day the ability to control a narrative is extremely important and DeSantis has shown to be good at that as Well
He followed the narratives set by Trump. He has yet to show that he can set a narrative in opposition to Trump and win out over the Trump narrative.