Why was gray cut, didn't they just claimed him from The Pats.
Several possible reason, and it could be more than one.
Gray was brought in as for intelligence and either refused (and was cut) or cooperated (and Fins have all the info they are likely to get so got rid of him).
Fins thought they were going to get a gem off of the Patriots garbage heap, and after closer examination realized that there was a good reason NEP got rid of him, so moved on.
Fins never really wanted him, but had heard the reports NE was looking to sign him to the PS so they figured just fuck with their rival.