Why is violence between Pakistan and Afghanistan recurring?

Pakistan has carried out new strikes inside Afghanistan. Once allies, Pakistan and Afghanistan's relations have worsened since the Taliban's return to power in Kabul in 2021. Tensions are fueled by accusations that the Afghan government shelters the Pakistan Taliban (TTP) and other armed groups responsible for attacks inside Pakistan, which Kabul denies. Efforts to stop the cycle of violence have failed, raising concerns about long-term fallout.