At least one weakness of the terrorism tactic is that its impact depends almost entirely on the opponent’s reaction.
The idea is to instill terror that is disproportionate to the practical damage done by the attack itself. The impact, therefore, is determined not by the perpetrator, but by the recipient of the attack.
For example, studies of the impact of the September 11th attacks estimate that potential losses due to direct business interruption caused by the attacks was around $43 billion in GDP, but actual losses were only about $12 billion. That means that the practical damage of the attack itself was a terrible failure in terms of the damage it could have potentially inflicted.
Indirect negative impact on US GDP, caused by fear (for example, losses for the airline industry) amounted to $50 billion. Almost 80% of the impact to US GDP was caused by the reaction to the attacks, not the attacks themselves.
What that means is, 80% of the impact of a terrorist attack is determined by the victim , not by the attacker.
That is an unreliable strategy. Effective tactics inflict practical damage directly.