Some people over-value the draft. How many players each year that come from the draft end up being great? Picking up UFAs atleast guarantees a sample pool of the players strengths. Having your multi-million dollar franchise/team tank for a higher draft pick the following is stupid, and hardly ever warranted.
BB references in interviews, the Art of War by Sun Tzu, in that you empower your strengths, and attack your enemies weaknesses. Certainly Brady afforded him a lot of room with his ability to make on-field adjustments, etc... BUT, that was assuming Brady as a strength. Now that he's gone, it changes. No better way to gauge how well a player performs in the NFL than looking to the UFA charts.
People saying the Patriots will tank are betting on a 50/50 gamble in hopes that they can say they told you so. Realistically, they're telling themselves that, because BB and co. make it more like 80/20 that the Pats will fair just fine without Brady.
We had no offense last year anyway, and still went 12-4.