Tether would account for 7.8% of all Bitcoin.
Not sure if that would count as being propped up. It's significant but not entirely propped up, there is a ton of real money in there too.
If I create 100 billion FakeCoins and sell one to my grandmother for $10, suddenly FakeCoin has a 1 trillion dollar market cap. It doesn’t mean there’s anywhere near that much money actually in the market to support that valuation.
If the tiny chunk goes, it all goes tumbling down?
stay far away from bitcoin.
There is zero money "in there" market cap for a non-backed currency is meaningless value. No amount of bitcoin buying will ever put money "into" anything. The money goes to whoever sells its just a trade.