Giving only three days and offering to assist with transfers could also point to the possibility that they really don't have that many paying customers to begin with.

Perhaps, but why shutdown the service so abruptly?

Why not shut down the service in, say, 3 months, support MyRedis customers to migrate to Redis Cloud (or elsewhere) before moving the MyRedis personnel into their new roles.

As somebody without any experience in the world of start-ups the only explanation I can come up is that MyRedis was haemoraging cash so badly that this wasn't feasible however if that is the case why would you want to hire the team?

Can anybody with experience of such dealings shed some light?

The employees can see how the customers are being treated. I expect most of them will be moving on, negating the acquihire.