Traditionally in the US, monopolies are managed by either forcing breakup/divestiture (the the company is already a monopoly) or regulating the maximum market share consolidation (preventing mergers which consolidate beyond that threshold).

And tech is different from agriculture. Governments will go overboard to prevent famine or hyperinflation of food prices because both with cause massive political and social instability. Tech doesn’t (currently) plan an equivalent role in our lives, so people could tolerate monopolistic behavior in tech longer than in core agriculture.

Being pro-markets and pro-capitalism is not the same thing as being in favor of letting companies run rampant with M&A with no consideration for market power or monopolization.