In very short- they did a lot.of shit to him, treated him like garbage the entire way, and then at the very end they literally tried to bribe him into being the scapegoat for the backlash they intentionally caused.
It's not unreasonable to expect a game to be, to the publisher's knowledge, bug free. In fact, it's not just reasonable, as a programmer, it's fucking baseline.
Most game devs are a fucking embarrassment, and they deserve to be dragged.
Because they turned away from the original founder's philosophy, which is that 'perfect security' is a pie-in-the-sky novelty that isn't actually useful to anyone, and what's actually important is security that people actually use. Even if it's slightly less secure, it's still a net positive because people are actually using it.
When he left, a google CEO took over and frankly it's just been one terrible decision after another- cryptocurrencies, 'stories', stickers, removal of SMS, all kinds of stupid shit that drove people away.
I used to have nearly 50 people on my signal contacts list. Now there are 3.
You'll notice Signal backtracked on supporting SMS as soon as they got an ex-Googler as their new leadership.