They only call it interference if it supports the wrong people. Russia taking out ads on Facebook: election interference. Various state sponsored media outlets and foreign politicians and officials disparaging Trump: free speech.

Rigging is a direct action on the election itself. Like removing ballots that were valid, submitting and accepting ballots of ineligible voters or straight fake them, blocking groups of people from voting (e g. blocking roads to voting polls), straight changing the numbers etc.

I see a distinction because all of the above are still happening in many countries, and there is a degree of illegality that is way above simple conning.

There's the other situations where people feel under threat of direct violence if they vote the wrong way. Perhaps there would be a different term for that altogether.

Do Russia and China have laws preventing their governments from interfering in other countries’ elections? If this all happened online, I’m pretty sure Romanian laws don’t apply.

It's not like they made the dead vote. They just used an unregulated vector of appealing to the electorate in a better way than the opponent did. I'm not saying it's not not rigging, as that's definitely the intent, but let's not turn a blind eye to what is an obvious thing