Indeed, there was an imperfection in the code which allowed for players that change teams within the same league to keep their accumulated MVP points from the old team. Since the teams global success does have a role in the voting, this enabled, as was in this case, for a player to get the MVP award even though he only had one game with the new team. I've fixed the imperfection and reran the voting, awarding your player the MVP award, as it should have been from the start.
The fix will be applied globally for the next season's MVP calculations, but until then, if there are any more such cases for last season, I can fix them manually, like this one.