Is Dave an usurper of power?

Although Dave, as President of the US, made undeniable good acts turn into reality, making us wonder why things don't always happen that simply, he can still be considered an usurper, as he took the chair of President for himself without being democratically elected.

So, in this case, given that Dave usurped the power, but did it so he could make the things that all the democratically elected Presidents couldn't, are his actions still morally condemnable, or, in this case, the ends justified the means?