The answer for that is easy: no, not at all. Portuguese expansionism in the Atlantic can be traced to well before the birth of Henry, and sea-based trade was a significant activity for the portuguese economy for a long time. In 1385 Portugal came out of a sort of civil war where a new dinasty was founded. This dinasty, of which Henry the Navigator is a member, by being the fifth son of the founder, owed a great deal of its legitimacy to the urban population. This created a particularily strong link between the monarch and merchants of Lisbon and other large cities, all firmly implicated in trade in the Atlantic. Yet, even in the previous dinasty, the kings of Portugal focused resources in naval construction and technology, and to some degree were trader-kings. A telling law of the time stated that if the king’s ships were harboured in a particular port no other ships could be chartered.

The portuguese navy had been reorganized by Genoese admirals in the first half of the 14th century, after trailing behind other Iberian kingdoms, most notably, Aragon. In 1282 the portuguese king married an aragonese princess, effectively establishing an alliance and improved contacts with the maritime power of the western mediterranean at the time. Portuguese ships were frequent all the way to Flanders and London, seen alongside english ships in the hundred years war and specifically used to raid the barbary coasts of northern africa or to defend the portuguese coast from likeminded moorish raiders. There were a lot of trends and forces pushing for portuguese exploration of the open ocean, and the first attested trip of exploration and conquest (albeit to the already known Canary Islands) is dated to 1341(or 1336), more than 50 years before Henry, the Navigator, was born.

Prince Henry, son of John I, was certainly a man of importance and his actions and decisions influenced the history of the world. But, at the same time, Henry, the Navigator is an image created by Great Men Theory. European voyages of discovery were neither a fluke nor the result of a single person’s effort. The technology that enabled the exploration of the West African coast and beyond is the sum of many parts: the latin sail (which is first seen in muslim vessels in the mediterranean), the spread of astrological knowledge by the universities (both in Castille and Portugal, the first universities were founded in the 13th century), the development of an original cartography science (born in the mediterranean, where coastal trade is common and folks need to know their coast), the viking/norman experience and naval construction. Christian Europe was also deeply involved in the fight for the control of the Mediterranean against Muslim North Africa, which stimulated naval investment, but because of this, the mediterranean was no longer its core, which shifted north to incorporate the north sea, and, by extent, the Atlantic. The Reconquista, still ongoing during the early Age of Discoveries, was a race for territory between the Iberian Kingdoms, and that expansionist pressure was not contained by the geographical limits of Iberia.

All these technological and political aspects have nothing to do with Prince Henry. He did push for exploration and invested in seafaring, but there was immediate profit to be taken in that, both personal and for the portuguese crown. And if there was immediate profit and successful investment had been done before, it is difficult to argue that sooner or later another one, in the same priviliged position, wouldn’t act in a similar way.