“Accidentally” is not accurate. He used AI to inspect the source and found credentials that work in all devices. He also never gained control of anyone else’s devices. He never used the exploit.

I didn't read the article but based on the title and subheading I assume they say "accidentally" because he was trying to reverse engineer the communication protocol to use his own device and he did not expect to find something as dumb as master credentials that would work on others' devices.

"Accidentally" as in his intent was to gain control of his own device but instead discovered what would in a just world be considered criminal levels of either incompetence or indifference to the most basic levels of security in the entire product line.