Asking for credit card details on a free trial is going to be a stopper for new users.
I've seen how much hard work and emotional energy they've put into their product over at least 4 years. And I've observed them go through a whole lot of different experiments on how to optimise their on-boarding process for new customers.
I can tell you that their current signup process has been tested and optimised to within an inch of its life, in order to get the outcome they want, which is to attract users who are serious about using the product and will be happy to pay for it as soon as they're convinced it does what they need.
As the article says and as another commenter pointed out, they now make enough money to pay both founders a modest monthly wage.
They don't sell advertising in the app, they don't sell your data, and they haven't taken funding. Every cent they make is from people who love their product.
Please believe me when I tell you they really don't mind when people are turned off by the requirement to enter payment details.
To be fair, though, I’m largely in agreement with you in this case. For products like cloud infrastructure, where the company is fronting real costs, the requirement makes sense to prevent abuse. But this product has low marginal cost per user, and also loses all of its value if a user recreates his account.
Unless, of course, you could import historial data somehow. But then maybe just make that feature not available on trial.