Edit: s/election/voting/
The election includes the whole primary system and the electoral college. Here I specifically mean the vote.
That's plenty for the seeds of doubt, especially given how easy it is to vote in several states.
I'm particularly interested in what types of machines and other voting procedures were in use there. It looks like they're optical scan machines, so hopefully they have the paper ballots on hand to do a proper audit. That, along with the voter rolls, should be able to determine what the issues were. That's a strength of using the optical machines as opposed to the purely electronic ones.
You're right that Detroit is just one city. It's also a city that's deeply troubled on many levels, so I'm not sure if it's fair to consider it typical. That's by no means excusing what look to be issues there. Those should definitely be looked into, and exhaustively. You're claim above is that there were enough fraudulent votes that Trump would have over 50% of the popular vote if they were removed. Detroit alone isn't enough to do this.
More important is to look at who's got owning shares in those machines.....
In the perfect world, we'd have open source machines that all enter voites into a public blockchain/ledger and you'd get a private key you could verify your vote with. Optical sounds awesome. But good luck with that. The fraud just seems to swing back and forth from left to right every X years instead. It's madness.
My claim is just a bet right now. But it's one I'm willing to put money on IF they actually do a national investigation, which I'm not confident will happen.
If voting integrity is something you feel particularly strongly about (I certainly do), I encourage to look into the work that's already out there. The 2000 election spurred a lot of research. Some good starting points are:
Ronald L. Rivest MIT
Auditability and Verifiability of Elections
ACM-IEEE talk March 16, 2016
https://people.csail.mit.edu/rivest/pubs/Riv16x.pdf
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Ben Adida Google Tech Talks December 19, 2007
Theory and Practice of Cryptography: Verifying Electiosns with Cryptography