Strange occurrence when fixing a radio

An odd thing happened today when I was fixing a Philips de Luxe radio from 1965.. How can the audio from my phone transfer to the radio? Not I did not use a Bluetooth device or overlaid the audio (my editing skills aren't that good!)
Camera/Audio;
GoPro HERO7 Black: amzn.to/2Lm1eDY
Ulanzi Vlogging Case: amzn.to/2WRcDkz
Rode VideoMicro amzn.to/2WTDTP7
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