My understanding is that Apple adapted the Xerox idea of a mouse and improved on it.
Doug Engelbart of Stanford Research Institute invented the Mouse, not Xerox... and Apple licensed it from SRI. The did improve on it. Some others added more buttons. Apple eventually accepted the need for more buttons.
My understanding is that Apple adapted the Xerox idea of a mouse and improved on it. But Xerox had the idea first but didn’t have the idea of what to do with it! Microsoft actually refined it for Apple that is how Microsoft got their Windows system!