The names in the log(s) are not a proof that they are different persons. That log, is only proofing that those are newly created account(s) - from one or different persons. Nothing more, and nothing less. Furthermore, on all this, we should believe on your word, which is, taking into account all the circumstances, hard to do. Openly or silently, calling student(s) to vote for a professor, is a collusion and "trading with influence". Will they, or not, take a part in some future contests, it is again, not a proof, but a guess. In exact matters, we do not rely on "guesses", but only hard-substantiated proofs and facts. As a professor in science, you should especially know that.
Let me educate you on the matter of promotion: Promotion is not cheating. Promotion is to disseminate the information in a wider possible circle, and not only to the one (circle) that brings personal benefits to you. In this case, ALLEGEDLY, you informed, your (!) students, to vote for your entry, en masse (!). That is not promoting, that is, as I said: UNETHICAL.
Yes, I deleted the vote for your entry, because I do not cast votes for someone who is UNETHICAL AND CHEATING, when I saw what you were doing... Politeness does not exist in science, rather, just hard proof and facts. Someone, like it, or not. Precisely, what and how, I have stated.
BUT, again, you are not alone - first 10 entries on leaderboard did the same thing (and again, excluding only MATLAB staff).
A collegial and benevolent advice - from a student educator, as well as you are: to students, you need to give your own rightful example, in the best light possible. What, and how, you learn them, they will behave throughout their whole life carriers. And, what you did, is not a good example.