It doesn't matter if it's based on the blockchain technology or some centralized technology.
Such voting systems can get hacked and manipulated.
Unfortunately the good old paper ballots are the still the safest way to vote(if the voting administration is out of the direct control of the government so the elections are fair).
The technology is still in the early phase and they just hurried it up to show something new to it's voters, afterall many things are going to be same it was for some time. A government built technology is often of low cost and quality and probably didn't wen through any penetration testing. But as they learn form the mistakes and keeps patching the holes, electronic voting system based on blockchain would be a norm within two decades.