Although there is no evidence one way or the other that the Soviet torpedoes had the same self-destruct capability as the US ones they were probably turned off.
Earlier, a Soviet torpedo fails to detonate when it strikes the Red October...due to "safety features" being enabled.
Capt. Vasili Borodin: Torpedo impact, 5 seconds.
[the torpedo slams into the bow of Red October and breaks up on impact]
Commander Bart Mancuso: I'll be damned!
Jack Ryan: What happened?
Commander Bart Mancuso: Combat tactics, Mr. Ryan. By turning into the path of the torpedo, the Captain closed the distance before it could arm itself.
Jack Ryan: So that's it?
Captain Ramius: Not quite. Right now Tupolev is removing the safety features on all his weapons. He won't make the same mistake twice.
Konovalov Crewman: Torpedo, Dead Ahead!
Andrei Bonovia: [to Captain Tupolev] You arrogant ass! You've killed us!
[just moments later, the Konovalov explodes.]
Of course, this is a movie construction for dramatic purposes...no such final scene appears in the original novel where, in fact, the Konovalov is literally rammed and crushed by the Red October.
The Red October rammed the Konovalov just aft of midships at a thirty-degree angle. The force of the collision ruptured the Konovalov‘s titanium pressure hull and crumpled the October‘s bow as if it were a beer can.
The Konovalov had had full watertight integrity set. It did not make a difference. Two compartments were instantly vented to the sea, and the bulkhead between the control room and the after compartments failed a moment later from hull deformation. The last thing that Tupolev saw was a curtain of white foam coming from the starboard side.