He was arguably more of a Fascist than the people who invented and popularized fascism. The only real difference between him and actual fascists is that he did nominally respect some of the boundaries imposed on him by the constitution.
Other than that though he had all the classic characteristics of a fascist leader. Using the state to control corporate power (the reverse of what we see today ironically), an obsession with war for wars own sake viewing it as an elevating force, a love of nature and its preservation (hitler especially was a staunch environmentalist), and as mentioned he was a charismatic populist.
There is also the traditional fascist idea of an enemy other or elite that he battled against>To destroy this invisible Government, to dissolve the unholy alliance between corrupt business and corrupt politics is the first task of the statesmanship of the day. This country belongs to the people. Its resources, its business, its laws, its institutions, should be utilized, maintained, or altered in whatever manner will best promote the general interest. This assertion is explicit... Mr. Wilson must know that every monopoly in the United States opposes the Progressive party... I challenge him... to name the monopoly that did support the Progressive party, whether... the Sugar Trust, the US Steel Trust, the Harvester Trust, the Standard Oil Trust, the Tobacco Trust, or any other... Ours was the only program to which they objected, and they supported either Mr. Wilson or Mr. Taft