There is a cost to cutting players. Jamie Collins would cost $11.9 M in dead money (in 2018) and give them $250K in cap savings post June-1 cut per the link you posted. Eating $11.9M in dead money is not smart business.
Coincidentally, trading Jamie Collins post June 1 would cost them $1.25M and save them $10.9M in cap savings. THIS and exactly this is why you saw many starters getting traded at the deadline. You also have players in the final year of their contracts and those teams knew they weren't going to resign them. Better to trade them then to let them walk for nothing or a compensatory pick that may or may not come in 2 years.
The Browns have almost $24M in dead money from other moves right now
Dead Money
Name Cap Number
Kenny Britt $4,875,000
Joe Haden $3,600,000
Jamar Taylor $2,000,000
Carlos Hyde $1,946,078
Danny Shelton $1,692,940
Corey Coleman $1,669,088
DeShone Kizer $1,304,133
Cameron Erving $1,279,376
Joe Thomas $750,000
Jason McCourty $625,000
Mychal Kendricks $500,000
Nate Orchard $377,055
Cody Kessler $332,394
Carl Nassib $222,438
Dan Vitale $222,353
James Burgess $218,118
Shon Coleman $216,884
Xavier Cooper $148,071
Devaroe Lawrence $141,176
Ibraheim Campbell $128,002
Jordan Payton $114,824
Jeff Janis $100,000
TOTAL $23,789,757