they seemed to adore him more than most native americans at the time
As you may be aware, Osceola was the leader of Seminole resistance to American military advancements in Florida. But to understand why Osceola got so popular, we must go back to the Treaty of Payne's Landing, where the government pressured the Seminole chiefs to relinquish their Florida lands and instead, move west towards Indian Territory.
While some Seminole Chiefs did sign this document, others were vehemently opposed to it. One of those men was supposedly a young warrior named Osceola, who was so opposed to the treaty that he stabbed the document with his knife in a show of defiance to the United States. However, this story seems to be more a myth than fact, as nobody recorded this incident (government records and eyewitnesses do not mention this) and the first artwork we have of the supposed stabbing is in an 1841 sketchbook that is full of historical inaccuracies. In fact, some think it was a different treaty (Treaty of Moultrie Creek) where he did this. Regardless, it is safe to assume that the legend had begun to make its way around the nation by the time of the Second Seminole Wars.
One of the striking traits of Chief Osceola's leadership was his oratory ability. Patricia Wickman writes in Osceola's Legacy that "Osceola appeared, to Indians and whites alike, as a strong voice...his power to persuade was observed by the whites, who quickly gave him more status than his cultural peers." It became noticeable that Osceola had gained quite the following of men willing to fight to the death for their land. When the Second Seminole War started, it became quite clear that his fighting prowess could not be underestimated either.
On December 28th of 1835, the famed leader killed Indian Agent Wiley Thompson and an associate outside of Fort King (Ocala). On the same day, a large Seminole force wiped out a column of 108 American soldiers marching from Fort Brooke (Tampa) to the relief of Fort King. Several days later, the Seminoles repulsed an attack by 750 soldiers led by General Duncan Clinch at the Withlacoochee River. Thus began the Second Seminole War, the longest, costliest, and deadliest of all the wars the United States has fought against Native Americans.
The United States government responded quickly and in force, but met with one embarrassing defeat after another. General Gaines came from New Orleans with 1,100 men in February of 1836, and wound up being held under siege at Camp Izard on the banks of the Withlacoochee for over a week before being forced to retreat. General Winfield Scott arrived in late March with 5,000 men and a grand plan of conquest, but spent a month conducting a fruitless, frustrating search for Indians that had taken to the impenetrable swamps and forests and refused to come out and fight. Governor Richard K. Call led several thousand men into the Seminole stronghold to the west of the Withlacoochee, only to be stopped by strong Seminole resistance at the Battle of the Wahoo Swamp. The Seminoles were proving much harder to subdue than anyone expected.
While the specifics of the later half of the war aren't relevant, the impacts are. The Second Seminole War was proving to be one of the costliest and most embarrassing military engagements the US had involved itself in. Many were shocked that the military was suffering defeats at the hands of people they thought inferior. John Mahon estimates that it cost the US $30,000,000 to $40,000,000 and 1,500 American deaths (though most of those were from disease).
In this sense, Americans didn't "adore" him so much as they did respect him. They realized that the Seminoles weren't just going to back down from a fight, and they thought this was in large part due to Osceola's leadership. In fact, the only reason Osceola was captured was because General Thomas Jesup ordered a false flag of surrender. When Osceola and fellow warrior Coa Hadjo arrived to talk terms of the surrender, they were arrested. Osceola was eventually moved to Fort Moultrie in Charleston, South Carolina where he would die less than a few months later.
With all this in mind, American attitudes towards Osceola can be seen as "respected" more than "adored". His oratory skills combined with his military success helped the public perceive him as an admirable foe rather than an uncivilized savage.
Sources:
Mahon, John K. (1967) History of the Second Seminole War. Gainesville, Florida: University of Florida Press
History of the Seminole Wars. Seminole Wars Foundation. 2012.
Wickman, Patricia. Osceola's Legacy. Tuscaloosa, AL: The University of Alabama Press, 2006. Project MUSE. Web. 28 Mar. 2014.
Osceola and Abiaka. The Seminole Tribe of Florida. 2014.