Quick side note, I’m not entirely sure how it became assumed that Abu Bakr II was the king in the Atlantic voyage story, since Musa himself says the “king who preceded him” which refers either to Mansa Muhammad or Mansa Qu, Abu Bakr most likely being Musa’s grandfather who never actually ruled himself.

The story you’re talking about comes from the Mamluk scribe al-Umari who got this secondhand from one of Musa’s hosts in Cairo during his famous Hajj. This is also, bizarrely enough, the only place this story has ever shown up. No other Arabic historians wrote about this, no oral traditions tell it, it’s literally nowhere else.

Which is suspicious - Mansa Muhammad and Mansa Qu we’re from an entirely separate branch of the Keita royal family, which certainly suggests a measure of intrigue at work. But that’s impossible to prove when we have just one source on the subject.

There’s also the question of technology: West Africans at this time had, according to Portuguese and Venetian sailors just a century later, dugout canoes made from hollowed our logs. While these were effective for fishing and river travel, it’s hard to imagine anyone sailing across the Atlantic in these boats.

But enough about qualifying the story, onto your question itself:

Unfortunately we know next to nothing about “Abu Bakr’s” motivations for venturing into the sea. Musa as recorded by al-Umari simply states:

“The king who was my predecessor did not believe that it was impossible to discover the furthest limit of the Atlantic Ocean and wished vehemently to do so.”

Curiosity, then, is Musa’s explanations. But historian Michael Gomez points out that this king set out on his voyage with ships loaded with gold. Why? Presumably as a means of exchange with anyone they encountered. Who did they expect to encounter, though? That’s hard to really tell at this distance with so few sources. Mali had traded extensively with North Africa, and by extension, Europe and the Middle East by this point. But Malians knew that those markets were to the north, so if they wanted to bypass the land routes why would they sail west?

As for what they know, it’s also hard to tell. Musa’s story tells of two voyages: one which set out and encountered “a river with a powerful current” which Gomez speculates is the Canary Current well off the coast of Senegambia where the Mansa presumably sailed from. The kings, however, did not believe the lone sailor who returned and told him of the current, and instead prepared a fleet of some 2000 boats filled with supplies, men and gold. And so he ventured out into the sea, leaving his cousin Musa as governor.

Nobody heard from that king again - leaving Musa in charge. So what do we make of this story? It’s hard to take it at face value truth be told, particularly because it works as an incredible front for Musa to cover any intrigue he used to gain the throne. At the same time, there are enough elements of truth and plausibility that it can’t be dismissed either - Musa seems to know about a massive oceanographic feature and how else would he know of it if nobody had seen it? Outside sources, perhaps, but it’s not conclusive.

Regardless, it’s one of the most colorful stories from medieval Mali.

Sources: Corpus of Early Arabic Sources for West African History - Nehemiah Levtzion and JP Hopkins

African Dominion: A New History of Empire in Early and Medieval West Africa - Michael Gomez