Black Isle was a studio created and owned by Interplay when Interplays funds were lost they layed off all the Black Isle staff and shut down the studio. Nothing really "changed" with Black Isle. When they were experimenting they gave the game to Micro Forte which was another studio owned by Interplay charged with making strategy games. The end result was Fallout Tatics which had the dark humor, and the lore. The only problem with it was it lacked the 1950's retro theme. So most of the fallout style weapons in the game were replaced with real life based ones. Tatics had weapons like the AK47, M16, M60 machinegun, M1911, M9, M113 APC, M4 Sherman, A Humvee. All of that was criticized by the fans.
However the game itself was fine as far as gameplay. So after Black Isle was shut down, Interplay got a new staff to make another Fallout game. The game sold poorly and scored very low ratings and eventually lead to Interplays downfall.