Sign into an existing account

If the company fires "most" of you, who will be left to do the work? Your company will have to stop doing whatever it is your company does and spend weeks hiring new people. They can't afford that.

Some people are spiteful as fuck.

Other people will literally murder you for what may seem a small slight but a huge one in their mind.

Lawyer up.

If he lied, and you didn’t do what he said you did, then the investigation will clear you. Who is investigating? Your employer, or the client?

Payback is a bitch
You only sight ONE SIDE of a story.
If it's that big of a deal post a link with company commentary as there are several words missing in this queef.
Never bank on one-sided stories like liberal fucks.

if you didn't do it, why would you get fired?

If the company loses millions by losing the contract and they know what the situation is, it seems like you wouldn't be fired. For the reasons that (a) you weren't incompetent and (b) they just lost millions and restaffing is a major expense for companies. If the company thinks its case is tight, then it should be going after the person slandering you and causing you to lose business. Perhaps in the event that your company isn't doing a good job of documentation, and its case isn't tight, then they're going to take a hit and try to make sure that hit is felt by the expendables.

Now, if it works out that the client agrees to keep the contract only in the event that a different team is put on the project, then that could mean relocating you and your team. If reassignment isn't feasible, then there could be terminations. But, this is a situation ripe for wrongful termination suits.

My advice would be to document EVERYTHING, carefully, and in more detail than you would normally think necessary (be meticulous). Request documentation from your higher-ups, and if they refuse, let THAT be documentation in itself. In the event of a termination, you need the evidence to tell a story that concludes in either or both of: (1) the reasons for your termination were unjust, (2) the company's procedure for handling your termination was illegal. If your company is large enough, they may settle out of court, and so even if you have to find a new employer, you will do it with a settlement in the bank.

it's a prank bro

You should all leave your cellphones at home and wear masks and gloves as you ride GPS-less bicycles to his house late at night and beat him half to death foe ruining your livelihoods and making your family possibly suffer hardships.

Sounds like your company doesn't know how to instill fear of blowback.

Companies have insurance that cover crap like this! IF they got the correct insurance.

Lookup "Vicarious Liability in Insurance":

I know you don’t wanna go into more details but it’s pretty impressive to me that he could potentially bring down a whole company.

This is why it's a bad idea to hire people who demand that they be called their preferred pronouns.
Or who make it a requirement that the staff not be allowed to say things like "Merry Christmas".
Or who demand that they get to dress like an idiot for faggot pride bullshit.

How much of your job can be done sitting?