Israel looks like it has all it can handle in southern Lebanon right now, as well as keeping a force in Gaza to maintain the 'ceasefire', so it'll be incumbent upon American Marines to go into Iran: a country larger than Iraq with a population over 90mn. Good luck with that Donald.A ground invasion was always on the cards, they can't defeat Iran with airpower alone.
Trump knew that all along but he didn't tell his supporters at the beginning because they may have not been so enthusiastic to start the war in the first place.
Getting into war is easy but getting out without losing face is difficult.
If Trump called off the war now, the Iranians would claim victory and be in an even stronger position than before the war, so Trump has no choice but carry on until the Iranian state collapses and to achieve that objective may require a ground invasion.
An assault on Iran would mean trump waving goodbye to any hope in the midterms, losing the Senate/House (or both) and becoming a lame duck for the remaining two years of his tenure. Go ahead Donny; make my day.
