Tell me: how did he know which employees were "weak"? How did he find out which of the ~8000 of Twitter's employees could be let go without risk of damaging day-to-day operations? Seasonal surges? Unpredictable news events? In less than a week? As a thought experiment, consider coming into a business of just 100 people, and firing 50 of them in the first few days. Could you do it with no risk? Maybe? If you get it wrong, you have to do what Elon did when he got it wrong and go, cap-in-hand, begging people you just laid off to come back and work for you. 
But hey, maybe you're both right and Elon knows what he's doing. Maybe Elon can continue to run Twitter with ~30-50% of its previous headcount, and not just keep it running, but develop new features! Maybe he's right, and he can work the remaining employees into the ground and replace them when they burn out - or offend him in some way - with no consequences! Maybe running a social media company requires the exact same skill-set as running a manufacturing company and that being an asocial oddball will help him somehow! Maybe selling $8/month subscriptions will offset all the lost ad revenue! Maybe users will gladly stick around while teen edge-lords and far-right nutcases spout racist, homophobic, transphobic, antisemitic slurs! Maybe this is all part of a 5D chess game that is inscrutable to a mere mortal like me and Twitter will indeed become the "premier app" (whatever that means) in a "couple of years"! And maybe tomorrow my morning coffee will turn to gold and my farts will smell of lilac.