It can be very easy to be fooled. There are a lot of scams, much more than legitimate tumblers, (unfortunately).
Some don't bother to create a website with a different TLD (.net instead of .com) and replicate the design of a well-known mixer in order to mislead people.
Others go further using the IDN homograph attack.
To make it simple they use very similar characters. For example, using "l" lowercase L, and "I" uppercase "i". Or "ẹ" instead of "e".

examples below: