Players have exit interviews with the front office following the season. The contents of these interviews are not made public so players are able to express their view of the direction of the team (i.e. the head coach) without fear of it making it into the press. If the situation was really as dire as Manish describes, this more than likely would have been identified during these interviews (if not well beforehand) and resulted in Douglas/ownership having no choice but to fire Gase.
I am aware of what exit interviews are. I'm curious as to your rationale that the Johnsons would have fired Gase after one season off the back of a few bad ones.
I'm also of the view that we have very few players who are good enough to have their NFL future assured, certainly at their current level of pay, and even in the supposedly closed environment of an exit interview it wouldn't surprise me at all if they were at least measured in their words.
Furthermore, if any part of what Manish has said is true, he wouldn't be the only one saying it. We know Manish has a vendetta against Gase. This has existed at least as far back as when Gase fired Manish's sources within the clubhouse following his ouster of Maccagnan (something Manish guaranteed wouldn't happen) and assumption of his duties. This was further evidenced by Manish's hostile line of questioning during Gase's press conferences and his apparent creation of a burner Twitter account meant to further discredit Gase.
We're honestly not far off the point at which your hatred of Manish becomes as equally dismissive a position as you seem to find mine of Gase, that your loathing of him so blinds you to the idea that he might actually be right that he could tell you that Gase has googly eyes and a slightly weird demeanour and you'd accuse him of making it up. Manish seems to have pretty much the same view as I do of Gase; he thinks he's a freaking awful head coach who should never have been hired and every day he stays here makes the team worse. I don't have a vendetta against him, I just want him fired.
The only difference between the plurality of fans who hold this view and Manish is that he has a direct line to Gase and gets to ask him the questions that we wish we could.