Just FYI for young football fans who might be on this forum, please don't be fooled by phony sports journalists. They make stuff up and pretend like they have inside information on who will be drafted by which teams. NFL teams, unless they have the #1 over pick, don't go around leaking out who they are taking in the draft. That could harm the team due to trading or other reasons. The draft targets remain a secret until the pick is made.
Cutting the 30year old Richardson saves the Browns $11 million in cap space, per Over The Cap, helping create some breathing room for the Browns after they signed Clowney to a one-year deal that can pay him up to $10 million but includes four void years to spread his cap number between 2021 and 2022. Because of those void years, Clowney's cap number for 2021 is just $3.87 million, less than a third of Richardson's cap number of $12.6 million.
With this considered, releasing Richardson wasn't entirely necessary. Cleveland still could have carried his contract and remained under the cap at a fairly comfortable margin.
But there is an advantage to be had with existing cap space when looking ahead. The Browns are approaching future offseasons in which they'll need to find cap space to re-sign Baker Mayfield, Nick Chubb and Denzel Ward. Carrying a healthy amount of cap space to the end of 2021 will produce a useful rollover number into 2022, when the cap is expected to jump significantly at just the right time for the Browns to spend in order to keep their own.