Please explain leverage to me

can someone explain leverage to me as practised by those RE bullshitters finfluencers. I feel their whole spiel is just bullshit but I don't know enough to be sure about it.

according to them, you "buy" a home - you put X% down and pay your first monthly (and then post on r/firsttimehomebuyer). then you go to (another?) bank and say "look I got this house I wanna use as collateral" and they go "wow you own a house! sure, have this bag of money"... repeat until you "own" like a city block.

like, how does that not crash and burn at the first step, just a cursory glance at the asset's status? how are they not "lol you ain't got no house dumbass come back in 20 years when you actually own it"?