Unions systematically destroy industries, and so are constantly looking for new profitable fields to exploit.
Companies usually end up with the unions that they deserve.
Tech workers were fine with the obscene pay they’ve been getting and were willing to put up with a lot. Forcing return to the office just to appease the international financiers may well be what forces the tech folks to join unions.
Pay well, and more importantly, treat people well, and there won’t be any unions.