Agreed, Suresh is clearly responsible for the disastrous 2016 financing.
Regarding Tom, I wouldn’t say so. “Challenging” could mean anything and thus fits perfectly with Tom’s careful and therefore sometimes vague expression.
I mean, what if you call something impossible and later someone proves to you that it would have been in fact possible? No, you’d rather stay on the safe side right at the outset and call it “challenging”. Then you are not exposed to attack.