The reason he has no “ground game” is GOP sabotage. Hence, huge rallies equals ground game. Get yer friends and relatives to the polls.
The presidential candidates raise money for this because it is important to keep close tabs and to be able to control your own campaign and destiny and run it as the candidate or advisers feel is necessary.
Trump chose not to do so. He chose not to raise money or self fund this part of his campaign to his own detriment. He told the RNC that he did not have the money to do it and asked them to do it. You go to war with the Army you have, as they say.
I have read that some states (Ohio), the RNC is running an excellent effort and everyone is behind Trump and other states, perhaps not as good (Penn).
No one really knows what this effort means on election day. Most say it is worth 1% or 2%, but in a close state, that 1 or 2 percent is everything.
So, you are correct. It is supremely important to get your friends and relatives to the polls and each one of us do our own get out the vote operation.
But never forget Trump is the one who made the decision not to run the operation himself and cede it to the RNC. He did not want to fund it and I'm sure he did it with open eyes since both sides have been shouting back and forth to each other.