It's Matt Stoller [0].
He tends to write his substack (and formerly his blog at the OMI under New America) in a very pathos driven manner in order to change the conversation around anti-trust.
He also seems to be trying to become a Republican Rohit Chopra (assuming Hawley climbs the ladder) and is competing with Oren Cass on that front.
There is a need to rework antitrust to take into account digital platforms, but imo Matt Stoller's attempts only serve to undermine the conversation, given that these are very technical conversations that have a high legal bar to pass. Going all "bull in a China store" a la Lina Khan only leads to appeals and out of court settlements in favor of the defendants.
Based on second-hand experience, now's the best time for M&A on that front - you're almost guaranteed to have the FTC fumble a case and settle out of court.
[0] - https://www.politico.com/news/magazine/2023/04/21/matt-stoll...