Wouldn't it make the most sense that BRK felt compelled, for one reason or another, to wait until the antitrust remedy decision was released?

BRK is in a particularly delicate situation with this sort of thing, given its standing in the political and financial press, etc., and if the order had required the dismantling of GOOG via the sale of Chrome or similar -- invariably sales that would have a political dimension -- being a significant shareholder would have brought BRK into the limelight. The dust settled and the purchases appear to have begun shortly thereafter.

There was also quite a bit of financial litigation risk pre-remedy order. I was a buyer but it was the kind of buying into the unknown that BRK does less of.

Alphabet is my largest position by a fair amount, including after substantial trimming post run-up (risk mitigation), so the seal of approval is good news in any case.