“Lots of gedolim said he wasn’t big in learning, including the Brisker rov”
The Brisker rav passed away 9 years into the Rebbe’s leadership, before the vast majority of the Rebbe’s talks were delivered and published.
Also, I’m not aware of anything negative the Brisker Rav – or any other gadol for that matter – had to say about the Rebbe’s Torah learning. Would you share with me, perhaps, what was said, by whom, and what source there might be for such claims. Who knows, perhaps you can also change my mind as to whether the Rebbe was a Talmid Chacham……