The banks went to the public for a bail out! Are investors investing in banks? Yes they are!
They need to crowd fund because they are in administration........ADMINISTRATION. They have no money.
A few million in donations is not going to sway investors you are right but that's not what it's about.
If something is up for sale what do you do? You show it to people! Getting them to the grid is more about advertising the team to potential investors on international tv and media. It's about showing investors that there is a team ready to race.
Your last point regarding 2015 is abit worrying but the way I've always understood F1 is that the following years car is already being designed and built halfway through the current season. So who knows how far they got with it eh?