When it comes to ancient history, circumstantial evidence is frequently all we can work with.
Despite what militant atheists think, we can't explain everything by doing a scientific experiment, pulling out our test tubes and beakers, or writing mathematical equations.
I don't believe anything about it, one way or the other. I stated that Bart Ehrman reports that some scholars think Jesus may have been capable of some basic conversational Greek because first century Palestine had been thoroughly Hellenized for three centuries, Greek was the lingua franca of the eastern Mediterranean, and Jesus was interrogated by Pontius Pilate who would not be expected to be fluent in Aramaic.