Or are you suggesting the elections are marred by fraud? It has to be one of these two.
But it's also possible that no viable oppositions are allowed to organize effectively enough to compete fairly.
My personal yardstick for judging a healthy and mature democracy is counting how many times political power has changed hands without violence -- Singapore is yet to score after 60 years.
The odds are stacked against the opposition — for some reason, elected Members of Parliament are required to manage their individual town councils as well. The opposition that won a group constituency recently got a lawsuit slapped against them for "mismanagement" [1].
[1] https://www.reddit.com/r/singapore/comments/dgbe25/ahtc_case...
Adding on: this is because the PAP in Singapore controls more than two-thirds of parliament [1], and have been able to push through constitutional changes without much consultation [2].
I think the increase in the private-sector requirement for candidates of our presidency (overtly disqualifying Tan Cheng Bock, a former PAP MP who was a candidate for the presidential elections, and is now the leader of an opposition party) slipped past many of our political critics until it was too late; a lot of uproar was focused on the elections being reserved for people from a specific ethnic group [3].
[1] https://en.wikipedia.org/wiki/13th_Parliament_of_Singapore
[2] https://en.wikipedia.org/wiki/Constitution_of_Singapore#Amen...
[3] https://en.wikipedia.org/wiki/Presidential_elections_in_Sing...