Disengaged voters will simply vote for the current leadership or loudest guy, typically the same thing, without a thought towards the issues.
Strongmen love compulsory voting, it creates a false perception of legitimacy, because corruption or no corruption, if only 30% of a population is engaged in the issues and the other 70% could give two shits, that is a slamdunk for incumbents.
There's some evidence for this. Chile adopted voluntary voting in 2012. According to this study[0] this decreased the incumbent's advantage in the elections that follower.
Strongmen love compulsory voting, it creates a false perception of legitimacy, because corruption or no corruption, if only 30% of a population is engaged in the issues and the other 70% could give two shits, that is a slamdunk for incumbents.