Name recognition gets him about 20% of the vote. He gets another 20% or so from people who don't like him, but hate Democrats more.
Getting that last 10% is the trick, and it's where all the money goes. In 2016, Hillary's campaign spent $564M and Trump $333M. This doesn't include outside PACs and such, but note that Trump only won on a technicality that year. In 2020, Biden spent $1,000M and Trump $774M, and Trump lost.
The GOP does need to collect donations. The 2016 Republican Convention cost $67M. They have $8M in the bank, which isn't even enough to cover the inflation on the 2016 number. State level Republican parties are outright broke. Oh, and some successful legal challenges to gerrymandering mean they'll have to back more candidates in races that are actually competitive.
There's danger here that Trump will win and be able to establish his dictatorship, but there's also a possibility of Republicans having complete electoral collapse outside of deep red states and districts.