There are a few issues here.
Arkadi Gaidamak (AG) is considered legit unless proven otherwise. Hence is money is OK.
I do not know weather his intentions are good, politic driven or else. However if you want to rule out actions that do good on ground of politic intention, then you will find difficult to approve any. Therefore I think that as long as his actions are good for the people, we have no right to stop him. If, for example, Stef Vertheimer would contribute 5M$ for the welfare of jerusalem citizens in order to become the next mayor, would this be bad?