Who poisoned Netscape?
There's a long list of companies that died by being acquired into a bad culture. OP is talking about the opposite: an acquisition so toxic it rots the parent company.
Netscape died because Microsoft bundled their browser with the operating system and made it free for commercial use, what essentially led to the huge antitrust case.
Only after that did browsers become utilities in the OS, with open source engines like Konqueror's KHTML (which later became WebKit, which later became Blink) and Netscape/Mozilla's Gecko