It’s very popular to look for off the beaten path answers for things like this. But seriously.
1. It wasn’t a right wing pro-Trump fanatic. Trump has never advocated violence. NEVER.
2. It wasn’t a patsy, carefully chosen by Deep State ™.
3. It wasn’t a false flag operation. (This time)
Sometimes the simplest explanations turn out to be true. This time it really was just a crazy guy who once wore a pro-Trump hat. Broken clock theory tell us it was bound to happen eventually. There’s no point going into deep conspiracies to explain the unexplainable. Crazy-stupid people never make sense to normal people. That’s why we call them crazy.
From limited information available, I’d say the guy in custody really did do what he is claimed to have done. Lock him up (after a comforting trial) and move on.