Fewer Expats Choose it Because it Is Further Away/Less Convenient, and Portuguese is Rarely Studied in US Highschools and Colleges

It never takes less than a 12 hour flight to get anywhere in Brazil if you are coming from the US or Canada. Whats more, you've got to go through the Sao Paulo airport and then get another continuing flight on to whatever your final destination city is.

If you are coming from Europe, only certain cities (ie Lisbon, Portugal) have direct flights to Fortaleza, Brazil. And if you intend to go to Rio, then the time it takes is back on par to what it is when coming from the US.  

The result is that going there and getting back is more of an ordeal. I'd wager that convinces nearly half of all would be long-term expats to choose a much closer location such as Colombia or the Dominican Republic, or Costa Rica for that matter. 

Many, many US citizens took Spanish in highschool.  Portuguese is a mainly unknown quantity among US educational institutions. College students often will have had a semester or two of Spanish: thus, Spanish-speaking countries like Ecuador seem culturally closer as well. Potential long-stay travellers rightly understand that a transition will be far easier when they already have some rudimentary grounding in the local language. 

Brazilians are More Individualistic than Most Spanish-speaking Countries

Without trying to answer the question of WHY this is, I'm quite certain of it and it is a significant factor which should lead you to consider at least giving Brazil a shot.  There is much less of a collectivist feel to Brazilian society than the Spanish-derived cultures of Colombia, Venezuela, Ecuador and the others. Again, I don't have to be able to explain exactly why that is to note the fact, and to have observed it in practice clearly.

It's rare that Brazilians will try to "point you out in public" as a foreigner. The Argentinians I've encountered living in Rio do, however. And I've lived for over a year in Colombia and another year in the Dominican Republic. Venezuelans strike me the same way.

Brazilians Have a Gregariousness and Honesty Which Feels very "American" to Me

In all the countries I have lived in (China, Colombia, the DR, Kenya, Russia, Brazil), the Brazilians are second only to we Americans in terms of general honesty (I am NOT referring to American ruling elites of 2023 and the deceitful, lying mainstream US media). 

This is a touchstone indicator of social morality.