IBM released it's Unix based AIX in 1986. I know, because I was there.
Long before linux was released, Unix System V was already well established and used by IBM, HP, DEC, Data General, Wang.
Linus Torvalds didn't invent anything. He ported already existing systems using Microsofts' x86 version of Unix they called Xenix as the basis for his Linux.
IBM has never tried to extinguish Linux. IBM have exclusively used and supported *nix based open operating systems longer than you've been born.
Linux, would not exist if not for IBM. It would not have grown to what it is today without IBM fully supporting and funding Linux development since the 90's.