The franchise that is the Maple Leafs also played in the 1st NHL season in 1917, but they didnt adopt the Leafs name until roughly a decade later. In fact they won won the Stanley Cup 8n that first season. No truth to the outlandish lies that's the last Cup they won, although it feels like it to those of us who haven't been alive to see it happen.
The story is a little convoluted but there was a dispute between the owner of the existing Toronto team and the other owners in the precursor league to the NHL.
Effectively they created a 'new team' but all the player contracts from the existing Toronto franchise were transferred. Basically it was a way to have the Toronto team in the new NHL, but get rid of the owner. Shame they never did that with Harold Ballard.