Terrorism is generally a losing strategy
Groups that have used terrorism against more conventionally powerful enemies have generally not gained an advantage.
9/11 was a disaster for the Taliban and Al Qaeda. The Taliban lost control of most of Afghanistan. Al Qaeda lost much of its leadership and had to go underground. It moved the USA in a more militantly anti-them direction.
Hamas rocket attacks and tunnels made Israel further restrict supplies into the Gaza strip. In the short term, Hamas has maintained control over the Gaza strip, but in the long run they haven’t gained any advantage in the conflict against Israel through attacks against civilians.
ETA has not gained independence from Spain.
The Tamil Tigers lost the civil war in Sri Lanka. All their terrorist tactics did was galvinize public opinion against them, and make the Sri Lankan government more dictatorial.
The Iraqi minority Sunnis broadly joined ISIS because the Iraqi government wasn’t representing them. They may have done half decently against the Iraqi army at first, but their terrorist tactics of mass killings galvinized Shia militias into arming in support of the government, and now that government is reversing ISIS’ gains bit by bit. And I doubt that government will get any more friendly towards Sunnis as a result of the terror tactics.
Basically, terrorist attacks cause fear, but they don’t cause paralysis. Instead, they cause reciprocal viciousness and a breakdown of civil society. Civil society generally favors tolerance of minorities. The point is that if you’re on the losing side to begin with, terrorism isn’t a winning tactic.
The exception to this long string of failures is using terrorism tactics to convince foreign armies to withdraw. The UK in Israel. The US in Iraq. France in Algeria. Russia in Afghanistan.