@bruceyg; for older folk like myself standing for a couple of hours in shoes creates issues ranging from aches and pain to poor circulation, edema and even to blood clots. He may even suffer from plantar fasciitis - very painful inflammation within the foot requiring painful injections of cortisone.
Trump may therefore have removed his shoes while on stage but after being swamped by security and being dragged off stage realised that without his shoes there may have been other issues with his feet.
Re Trump's comments about global conflicts and all of which he attributed to Biden's Administration, he was messaging anyone watching his speech that if he's elected in November the rules of engagement will be very different afterwards - he asserted that his actions will quickly end conflicts including those in Ukraine, Taiwan and the Middle East.