Adding to the other comments, even when certain fruits can indeed be grown in places besides California, there’s also the matter of infrastructure. Not specific to oranges, Pacific Fruit Express (PFE) supplied refrigerated train cars for long-haul distribution of fruits from California’s Central Valley out to the East Coast. Because this was the early 20th Century before mechanical refrigeration was widely available, cooling had to be done using the same approach for centuries: ice.

In this regard, California was blessed with the Sierra Nevada mountain range, where water could be frozen into ice and then transported by rail on the now-Union Pacific transcontinental railroad to Sacramento and then down to the entire Central Valley for keeping food from spoiling during the long journey out east. The fact that these fruit-laden railcars had to go through the mountain pass again meant they could be topped up with more ice, and when the empty train car returned from the East Coast, it could carry ice back down to the Central Valley again. A virtuous cycle.

Basically, fruits not only need to be growable, but also the transportation infrastructure must exist. Sure, Florida also had railroads in the early 1900s but it was not really well connected to the rest of the Eastern Seaboard. As a side note, this is a contributing factor to the Confederacy’s loss in the American Civil War, since different railroad gauges meant they had more difficulty mobilizing by rail, specifically for materiel. Whereas the industrialized North already used standard gauge everywhere for their mainline trains. So even if Florida did have standard gauge going into the 1900s, the different rail companies involved would not necessarily have had good enough relationships to easily schedule the necessary cargo trains to do a full run from Florida to the population centers up north. These are all frictions that never plagued the now-Union Pacific, which could run basically effortlessly from California to Chicago and eastward beyond. And of course, Florida is not known to have ice-making weather.

And now with an advantage of over a century, with the California fruit industry already built up, what would be the point to build up the same infrastructure but in Florida? It would be expensive and there’s no need for it, not unless California is about to secede from the Union.