Arizona was a well known swing state long before November, with most signs pointing to a Biden win. Biden also outspent Trump by twice as much during the campaign knowing it was ripe for the picking. Biden also spent more money in Phoenix than in any other market during the final six weeks.
As for the 2012 comparison Dick Morris makes, remember who was on the Republican ticket back then: Mitt Romney. Arizona had (and has) a large Mormon population. In 2008 they represented about 4% of the state, but 11% of the vote. I can’t find the stats for 2012, but I guarantee it was significantly higher with Romney on the ticket. In other words, they accounted for a very outsized proportion of the vote.
Meanwhile you have prominent Mormons like Romney and Jeff Flake (from Arizona) opposing Trump. In 2016 Mormons rejected Trump in unprecedented numbers. And one poll showed it was almost exactly the same in 2020. On top of that you had prominent Republican Cindy McCain (Arizona) also urging voters to reject Trump.
On top of all that, since 2012 Phoenix has been one of the fastest growing cities in country, largely from young tech types who tend to vote Democratic. So it was really no surprise that Phoenix and Maricopa county had a large change in voter demographics.
If you had been paying attention even long before the polls opened Maricopa county was often discussed as one of the biggest demographic shifts in the country away from Republicans and particularly from Trump.
Honestly, this wasn’t a surprise. It wasn’t ballot stuffing. Dick Morris can throw out some stats without any context and claim whatever he wants. But this was not some crazy thing out of left field that could only be “explained” by ballot stuffing. That’s just bunk.