You presumably used the reduced 2,300fps load mentioned in the other thread, meaning your 300gr Accubond arrived at just over 2200fps at your bull. You essentially hit him, and very lethally, with an enlarged .30-30. The lack of reaction happens a lot with moose too, have even seen them start to feed again, then fall over. Much as I like .375s there is no difference in what would have happened with .30-06, .375, or .458. My last three moose seasons were harvested with 7x57, .375 H&H, and .308 Winchester in that order with no difference between them, all died promptly.
This said, Ted / Why Not? who has seen more moose die than just about anyone on here has posited several times the most dead right there moose kills he's seen from a round come from the .270 Winchester. Get the speed up on your .375, load it more appropriately for moose with a 235, 250, 260, or 270gr much faster and your game tipping on the spot will increase. You can't count on it, just plan to see more of it the faster your bullet meets the moose. You'll also see more meat damage, a natural side effect of more violently dumping energy into an animal. You most definitely do not need a .416 Mag to take moose reliably, you could easily hunt moose all one's life with a .25-06 and no issue.