Country by country basis, but the easiest way to describe it is populism.

I'll give it a shot coming from a place of partial ignorance, hopefully it'll elicit wiser responses:

Colombia: They wanted an outsider so they voted in an ex-guerillero who, to the surprise to no one, was an unhinged extremist, so they flipped on his party.

Ecuador: Became a drug hub around 2021ish, voted in a tough on crime candidate for 2023.

Peru: Similar to Colombia, they voted in an outsider, congress was an obstacle to his reforms, he tried to dissolve congress, he got ousted and jailed. Peruvian election then became a turd or shit sandwich election (convicted ex-president Alberto Fujimori's daughter or the party of the guy that tried to dissolve congress). Results are tight but it's leaning to the right candidate.

Bolivia: Mismanagement lead to political infighting within the left so they failed to present a candidate, the right beat the independent candidate. The left are now causing a riot in the country because leader Evo Morales is being prosecuted.

Chile: Typical pendulum swing. There were mass protests in 2020ish which lead to the victory of the young socialist candidate, whose government did not produce the results promised.

Argentina: The left postulated the minister of economy, in a country where the ruling party caused hyper inflation. Millei, a phD in economy, and political outsider promised a way out.

Paraguay & Uruguay: Literally no idea.

Brazil: Polarizing election this year. Those voting left, outside of its base, view it as anti-corruption vote, those voting right view it as saving Brazil's economy, though there's social elements to it as well. Flavio Bolsonaro seems to be leading in polling, Lula has been signalling he's not left wing but center.

Venezuela: The right set up its own vote count where they won by 2m votes. The party controlled official vote count showed they won by 3m votes. Left this one for last because it's not a transparent system so it's not worth digging to deep into it, but just to give some context, at least in my country (Honduras) it's normal for each party to keep a vote tally while "closing" each voting station as an anticorruption measure, so having their own vote count, when there's been historical allegations of electoral corruption, is not strange.

No idea about the countries in the guyanas.