Bernstein did more than anyone to bring Mahler's music back.
Nonsense. Karajan and the Berlin Philharmonic.
I haven’t watched that video yet. But there is an amazing one of him conducting the choral finale to Mahler’s second. It is just awesome as he envelops himself in the emotionally charged music. He brings the listener along with him. Truly amazing.
And as you note: what would the status of Mahler be without LB? Probably still waiting to be re-discovered and that would be tragic.