No body is stupid to carry out a terrorist attack in order to force the whole country into negotiation. If you are taking inspiration from US-Afghanistan-Taliban, it took them over 15 years!!
The attack was not to force anyone into negotiation but only to provoke and derail any such planned process. AS
@scorpionx have correctly pointed, this will not put any chances of peace and negotiation into cold storage for a very long time. Perhaps this is what some wanted as it help them push forward a personal agenda and secure personal gain.