Why is it bad to use multiple if statemets when it's for the same statement?

It's two part I would say. One for readability, making your code easier to read and understand. There is also the part where if you have one if statement with several conditions, your code could execute faster.

Example:

// Example one
If (bool1 && bool2 && bool3) {
  // Do something
}

// Example two
If (bool1) {
  // Do something
}

If (bool2) {
  // Do something
}
If (bool3) {
  // Do something
}

// Example three
If (bool1 || bool2 || bool3) {
  // Do something
}

In the first example, say the first bool is already false, the Java compiler can already stop checking the if and move on. While in example two, it will check each and every statement, using more time and potentially making your app slower (This is relevant for much larger projects). The same idea for example one can be applied to example three, if the first statement is true, the Java compiler can skip checking the other conditions and execute the code inside the if statement.

I hope this explanation made it a bit more clear on why you are encouraged to use more conditions rather than if statements, especially in Craig's example of blocking bad words.