Maybe the country has the largest ecosystem because there are a lot of people in there. That doesn't imply in high quality, positive ROIs etc. Lots of people are just trying.
The country has some decent universities, some large and rich cities (despite the country, being, on average, poor) and some entrepreneurial attitude.
The drawback I observed the most is the same @cscotti pointed out: the people who end up creating companies are not particularly well suited for that. They want quick money out of outrageous profit margins - they are often already rich, but think they are entitled to more. It's the Brazilian version of the robber baron standard, but in a fractal pattern almost down to the bottom.
And, now, there's also the crazy politics (thanks, Obama) with a coup and all those shenanigans.
Brazil absolutely was a Baron country for most of its life (except they were more commonly called Colonels or Captains). Starting on the 16th century the Portuguese kingdom would distribute land for agrarian usage, and the Barons not only owned the land but its ownership was also hereditary. An intricate taxation system was developed that stimulated lang aggregation and so not long after you'd find many of these land owner families owned immense tracts of land - larger than cities or states, and became very rich.
As centuries passed, this system of power persisted, and there is still very very old money in Brazil. Many of these families would give tracts of land away for poor people in exchange of political support, and so they grew into the national political scene. Numerous past presidents came from these families (such as Sarney and Collor).
In short: Brazil has a longstanding colonial culture that persists even though its population might not be aware of it. All its symptoms are still there, including distrust in political entities, assertion of political power by intimidation or populism, archaic taxation systems, and a general sense of powerlessness to change things.
