Market awareness of the challengers is so low that I doubt that a high proportion of people who do end up using a challenger are aware of the others so they don’t end up comparing them. If they do find out about them & go with someone else then, as I mentioned, it’s not going to make a dent in the overall number of signups.
Also, one challenger always has things that the others don’t & vice versa. None of the challengers should be copying features just to maintain parity because that’s impossible to achieve, if they end up developing the same features anyway because they’re going to add the most value to customers & potential customers then great.