Going with the assumption that the Gauge is reading correctly and the Oil truly is hot ...
Stating the Obvious ...
The Oil is hot either because it is absorbing extra heat OR it is not being cooled.
Heating
The oil is heated to approximately the same temperature as the cylinders and should be nearly the same temp as the coolant.
The Oil gains extra heat in the sump as it contacts the hot bypass gasses from the piston ring blowby.
If there is excessive Blowby, there will be excessive heat.
Perform a cylinder compression test to see if you might have a leaky cylinder.
Cooling
The Oil thermostat is a simple but often misunderstood device.
Its flow paths resemble the letter "H".
The two sides of the "H" are Always open.
The Oil flows from the Oil Tank into the Top of one side and straight out the bottom to the Oil Cooler.
It then returns to the bottom of the other side and straight out the top and returns to the engine.
All the action happens in the crossbar of the "H".
At lower temperatures, the Thermostat is OPEN allowing the Oil to partially bypass the Oil Cooler.
Some Oil continues on through the cooler, but the majority takes the shortcut.
This design is Fail-Safe in that no matter how the bypass element may fail, the engine will always receive full oil flow and never become oil starved.
If the thermostat does not close, The hot oil will bypass the cooler and the engine Oil will run Hot.
The Oil Cooler will still have a portion of the Hot Oil Flowing through it so do NOT expect it to feel cool even though it is mostly out of the circuit.
Measure the temperature of the return hose from the Oil cooler, Before and After it passes through the Thermostat.
If the two measurements are close to the same, the thermostat is CLOSED and the Cooler is Working.
If the two measurements are significantly different, the thermostat is OPEN and the cooler is being bypassed.
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You mentioned that you Cleaned the Thermostat.
Did you disassemble it?
Did you reassemble it properly?