USDT, TUSD, BUSD, and USDC are all stablecoins. They have a value that is tied with the US dollar at 1:1 ratio. Now I'm wondering what is their differences.

• Does each of them has different purpose other than being tied to USD?
• Do they have different features or the fees when using them is different from one another?
• Why USDT is commonly used when trading other crypto not the others?