We're starting to get some political alignment on anti-trust against Amazon at least. Though one party seems motivated by worker/consumer right, the other by retaliation for Bezos' ownership of WaPo.

The various Standard Oil split results had some nice successes, too.

Honestly I'm not sure of the main corporate opposition to anti-trust other than ego and/or laziness. It'll force the resulting business to get even better. If you got your position by being the best, you can still be the best in the new world.