Trump has more experience running things than Obama did. Whether you think he did a good job or not is another debate. Obama went from a community organizer to a freshman congressman to immediately pushing for his presidential run. He almost never participated in votes or bill creation etc. He was a product of the system. A product of a system in which his party groomed him long in advance for the presidential nomination. Trump is about as far from being part of the "system" as you can get, which is why he is so appealing to so many people.
The issue wasn't that Obama had no experience in politics, it's that he ONLY had experience in the political game and none in actually leading or running anything. Trump has no political game experience and a TON of experience leading and running things. That's why his supporters like him.
The system sucks. We are in a shitty situation with Obama. We would've been in a shitty situation with Romney too. We will be in a shitty situation with Rubio or if Bush #3 wins. We will be in a shitty situation if Clinton wins. It's not that they're all bad people or don't have good platforms, it's that they are part of a really shitty system that gets shittier every cycle.
You may think that all Trump supporters are stupid thinking that they all actually agree with everything he says, but most of them actually just want to end the shitty system before it gets even worse. It's better to take a hit now to try and fix it than find ourselves in an irreconcilable situation in 20 years.
The bigger issue is that we are in a system where people vote without being informed on issues and that congress maintains a ~96% re-election rate with a ~11% approval rate. Yeah it would be better to start fixing things from the ground up, voting in good people and replacing the bad eggs from mayors to governors to the house and the senate and then the president, but that's just not going to happen. People are fed up with the system. Voting for Trump is a vote against the stupid political game MUCH more than it is a vote for the actual candidate.