I don't know about being against drugs. I'm betting that was just good PR.
Anyway the story I read was that his counselor, Anthony Caponigro (Tony Bananas-who was not a normal counselor in that he had his own power base and rackets) was upset about the supposed expansion of NY power into the Atlantic City rackets and/or was just convinced that Bruno was weak and now that Bruno's friend Gambino had passed away a few years back there would be no repercussion to removing Bruno.

Even so Tony Bananas supposedly checked with Frank Tieri, (front) boss of the Genovese family, to whom he was close, even though they had had a dispute about numbers/gambling rackets in Newark a few years back. Allegedly Tieri gave Tony the greenlight.

So Tony had Bruno clipped. Then the full Commission summoned Tony to NY for a hearing. It seems probable that Tony pointed to Tieri and claimed he gave the OK but Tieri was like "Who me??" whistle

Since people always believe a boss over a non boss and most people didn't want others to get the idea they could remove bosses they didn't like the ruling evidently went against Tony B.

Tony B. was found in a car trunk in the Bronx, stabbed , shot and with money stuffed into his nether regions. And the Genovese family took over the disputed Newark gambling rackets.

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.