Any time someone acquires a team, it is not simply a matter of buying a company. Members of that team can quit anytime they like. Acquiring a team means showing them enough money that they are willing to stay after the acquisition.

I do not know the terms of this particular deal but the rule of thumb is that acquiring a good engineering team will cost $1-2M per head. Some of that will go to investors but a big chunk of that will also go to the engineers as an incentive to stay on.