This is a tactic used to maintain power - delay elections indefinitely. Currently it’s happening in a number of African countries.

Undermining the credibility could therefore accomplish “everything” (the intended purpose).

Being able to sabotage elections and force a rerun might be an accomplishment for somebody.

For example a foreign entity could use this to cause confusion and undermine people's trust in elections.

I'm pretty sure if I get the election thrown out and smear my likely to win opponent as someone doing this kind of tampering it's all good.