I am living in rural Madagascar and realizing that every act towards developing this country and others like it into a more healthy, populous, and economically empowered place is an act towards industrializing its animal agriculture into factory farms and ensuring millions more meat-eaters. I have heard the argument that anyone who cares about animal welfare should focus entirely on animal causes rather than more inefficient human causes, but is development of negative utility in terms of the suffering it causes?

The name is much older than this, though it has generally been refered to as 'The Poor Meat-Eater Problem' which I think is a better name; I remember discussing it in 2012 and I don't think it was new then. On the forum with a quick search I found this from over 9 years ago.
I think it's quite plausible that over the last 10,000 years the benefits have not outweighed the costs.
It's also plausible that the next 10,000 years will be dramatically better - for humans, farmed animals, and wild animals. Further human economic development will be necessary to build the knowledge and resources to fully enable this.
But this doesn't address whether supporting economic development of developing countries right now is a net benefit.
That's not really an argument at all. How do we prevent future suffering? Is enriching the global poor in line with that ambition? I can think of ways that it isn't—that it will lead to increased suffering. A counterargument would evide that global development will not lead to increased suffering. That we like having undergone development ourselves is not a counterargument and does not imply that funding global development is of positive utility.