the main causes of PTI defeat are:
1. Imran khan focus only on PML n and not PPPP which was main culprit, so people thought that he is with Zardari
2. He only focused on youth and not on the mature and poor population of pakistan
3. His main focus was on the urban areas and he ignored the rural areas which comprises the majority of voters.
4. In few constitiencies there was reports of rigging which also played role in defeat but that was not such a big factor.
Maybe Imran miscounted the youth. There is more youth in rural areas then in urban cities and we all know who rural vote for. Imran didnt have strong candidates in rural areas like in 4 constitutions of skp there were 4 very very strong candidates that didnt get tickets Saeed virk, mian khalid, abid chatha and akbar khans son. Silent voter majority.
Could be many reasons. Dont really know bcz we can just speculate.
Pakistan lost is chance when it refused Ayub's Basic Democracy system. In a feudal, semi-feudal and partly tribal society how can Westminster type work? It will never. People will continue to vote as prodded by the Khan / Malik / Nawab / Chaudhury. Family-cracy or graft have no meaning to rural masses. Basic Democracy would have institutionalized a kind of semi-fascist rule that would make the country progress.