Barbados in the 17th century British Empire was more or less synonymous with high risk, high reward. It was one of the most profitable colonies of the British Empire, owing to its fertile soil providing excellent opportunities for growing cash crops, such as tobacco and sugar, which was largely accomplished using slavery. These fetched a high profit in Europe, and was seen as a relatively easy way to make a fortune.

The downside to this comes from the fact that Barbados was highly dangerous for young Europeans, due to the presence of tropical illnesses for whom few Europeans were prepared. Especially the yellow fever, which became widespread at least by 1648, had high mortality rates for people who hadn't contracted it during their childhood. This helped create and unhealthy disease environment with high mortality rates for Europeans settlers, who therefore did not seek to settle down in Barbados long term. Rather, they sought to make as much money as possible in as short a timeframe as possible, and then go back to somewhere more livable, such as Europe or North America, with a fortune to settle down with.

This also meant that there was a general labor shortage of the island- before the slave trade truly got underway, mostly white laborers were used, many political refugees from the English Civil Wars, and some men were straight up abducted and brought there - a process widespread enough to be called "barbadosing."

In other words, people who came willingly to Barbados did not come with the intention to stay, but rather with the intention to make a lot of money in a short time, and then leave as soon as possible. Naturally, the risk of the diseases did somewhat reduce the competition, and increase your chances of financial success if you did manage to survive them - this success was achieved by planting tobacco and sugar and exporting it at a high profit.

I am not one to tell exactly what your ancestors hoped to achieve in Barbados, but it would somewhat make sense that Wymond, even having a pregnant wife, did the voyage hoping to come back with a fortune to provide for his family. As he died there, probably of yellow fever, it sounds unsuccessful. That his pregnant wife didn't join him there is unsurprising, as very few European women went willingly to Barbados - as explained, the men didn't go there to settle down, but to make a quick fortune and come back, and bringing wives or girlfriends there would not help achieve that.

As you say, leaving your pregnant wife on such a risky adventure seems haphazard, so the possibility cannot, without knowing more details, be discounted that Wymond went to Barbados unwillingly - in other words, that he was abducted from Massachusetts and "barbadosed" by someone looking for cheap later and unable to find it willingly. Without knowing more details its hard to say. Either way Wymond was clearly not one of the lucky ones.

You can read more about this in:

Cray, Aisnley, From paradise to Plantation: Environmenal Change in 17th Century Barbados, a MAster thesis form Salem State University, and in

Jordan, Don, Walsh, Michael, White Cargo: The Forgotten History of Britain's White Slaves in America, New York Universirty Press, 2007