But as comments have said, even acknowledging interference after the fact and rejecting the result is a failure in democracy, because it's ripe for abuse. Thus, the Russian interference has still succeeded.
Citation very much needed. It seems you're desperately arguing towards a pre-determined conclusion. Especially if you're then equating this with a foreign government successfully installing a puppet regime.
Chances are he’ll be jailed or otherwise prevented from running.
If the evidence was serious it also would not make sense to let the election continue.
Finally I don't know about Romania, but in a few other countries in Europe, no matter what happens to that sullied candidate, these votes are not too likely to shift to the incumbent party. See for example the circumstances that enabled Macron to be elected the first time in France.
If the success is limited to repeating the first round of voting, that's a lot of Ukrainians who will still be alive next year.