It looks as though https://github.com/adafruit/MAX6675-library bit-bangs the SPI pins.
You have chosen the HW SPI constructor for the TFT.
Adafruit_ST7735 tft = Adafruit_ST7735(TFT_CS, TFT_DC, TFT_RST);
I suggest that you try the SW SPI constructor. The TFT will be a bit slower but the two libraries should not interfere.
Alternatively use separate SPI buses or just put the MAX6675s onto regular GPIO pins. You can share SCLK and thermoDO but need separate thermoCS pins.
Note that https://github.com/zhenek-kreker/MAX6675 is designed for proper HW SPI.
It really annoys me about Arduino libraries is when someone Forks a library, makes improvements but continues with the same class name.
In other words. I don't know which particular MAX6675 library you are using.
This also explains the nightmare with different LiquidCrystal_I2C libraries.