Reason for defeat of ibrahim lodi was that the whole country was not satisfied by the discission made by lodi of replacing the old guards with new soldiers. this hurt the old one. so this gave a chance to babur to attack and invade india

There were many reasons , first off all ibrahim's faulty strategies , he used elephants at the battle field which contributed to nothing but slowing down his army before the swift cavalry based army of ZAHIRUDDIN MUHAMMAD BABUR . second is, babur had the advantage of advanced artillery i.e.  guns and cannons, over lodi's army.he managed to get guns from iran. third was that babur's fierce "tulughma" tactics of warfare whisg gave him the edge and this is how the numerically superior forces of the lodi ( nearly 1000000, 100 elephants) was defeated by  the numerically inferior troops of babur. Also , it's to be noticed that the lodi sultan lacked mass support, basically of the rajputs under rana sanga who were themselves obsessed with the desire of becoming the rulers of delhi, taking advantage of the situation of political turmoil
another point to be mentioned is that babur had paved his way clear to delhi not at a single campaign but at 4 seperate campaigns by capturing bhira,lahore,dipalpur, one after another .
babur also had the experiece of fighting wars through his frequent battles with the uzbegi warlords of his homeland, Farghana 
HOPE IT HELP'S MY DEAR ! ! ! ! ! ! !