You’re right, meddling with elections in other countries has been done pretty often (see how many times the US appear in this list on wikipedia ) but sitting Presidents usually pretend to be politely looking the other way.

What’s different now is that Trump likes to put his name on everything, preferably in big golden letters, and he can’t keep his mouth shut to save his life. In the news it’s hardly ever “the USA” now; it’s “the Trunp admin” or just “Trump” doing everything.