I don't know how you can make that statement unless you know something that is not public knowledge.
To repay your investors if it doesn't work out is class (though they say it was from 'money in the bank', it is very well possible that this was simply the easiest way of liquidating the business and that the founders let their share of the payment due to them go), there is no doubt about that.
But the fact is that this didn't work out, how the next project fares remains to be seen.
Past failures are not a guarantee for future success or something to that effect.
What impresses me most about this farewell note is that they decided not to go for mediocrity but instead decided to pull the plug.
That takes guts, and is on par with the repaying of the investors (which is relatively easy if you have the $, otherwise it is much harder and even more classy).
Probably through personal experience, Ive met Sumon a couple of times and would happily take bets on him being part of something successful.
> I'm pretty sure the investors would rather have their money back than nothing at all.
Did you ask them? Are you yourself a VC investor? Its rather possible that investors saw promising talent and wanted to buy 2 years of their time.