Yet empirically, the biggest funders of basic research have historically been monopolies. The US government was, at least up until the last few months, the largest funder of basic research globally and it obviously maintains multiple different monopolies, a monopoly on legal use of force, a functional monopoly on financial transactions as the global reserve currency, and I'm sure others. Excluding national governments, Bell Labs and IBM were both probably the biggest funders of basic research in the last century during their respective heydays. Bell was obviously a monopoly and while IBM might never have faced anti-trust penalties, they did at one point control 70% of the mainframe market and the DoJ did bring a case against them (that was eventually dismissed by the Reagan administration.)
I think there are many good reasons to pursue anti-trust action against companies that are in a dominant market position, but we should be honest about the tradeoffs. Businesses that have to aggressively compete to maintain market share don't have the slack to fund basic research.