It is not a matter of out thinking the room.
Belichick inherited Bruschi, Ted Johnson, McGinist and Slade
In 2001, we had a need at LB. We brought in Phifer, Vrabel and Cox.
In 2003, we had a need at LB. We brought in Colvin.
IN 2005, we had a need at LB. We brought in Beisel and Chad Brown.
In 2006, we had a need at LB. we brought in Seau.
In 2007, we had a need at LB. We brought in Thomas.
In 2008, we had a need at LB. We drafted Mayo and brought in Seau & Colvin.
In 2009, we had a need at LB. We brought in Banta-Cain.
The patriots have not developed a LB this decade.
Perhaps Woods, Guyton, Redd, and Craig will be the exceptions.
Perhaps Crable, like Mayo, is a top talent that need little development.
If all goes according to plan, Crable will start this year.
I think the picture you paint is incomplete.
In 2003 we aggressively signed the top FA OLB out there, Roosevelt Colvin. He had some problems adjusting and then got hurt, and took 2+ years before he started producing for us.
In 2004 BB passed on one of my binkies, Karlos Dansby, at #32 in favor of Ben Watson. I think that hurt us.
In 2005 BB drafted Ryan Claridge from UNLV in the 5th round, who was considered a solid prospect. He had personal issues and never played for us. I personally think that BB had his eye on Lofa Tatupu and would have taken him at #64 (he was projected as a 3rd-4th round guy) but Seattle shocked everyone by "reaching" for him at 45 and we traded out of the 2nd round. BB clearly was mistaken in his assessment of Brown and Beisel, who were too slow and/or clueless to play in our scheme.
In 2006 a lot of people thought the Pats would take Bobby Carpenter, who Mel Kiper compared to Mike Vrabel, but Dallas took him at #18 and he has been a bust. We passed on Manny Lawson at #21, and he hasn't done much either. We drafted Jeremy Mincey in the 6th, but he got beaten out by UDFA Pierre Woods (who had been projected as high as a 2nd-3rd round pick prior to his senior year but fell into disfavor with Lloyd Carr at Michigan). Our LB corps clearly began to show it's age, most notably in the AFCCG against Indy. BB immediately went out and signed Adalius Thomas.
In 2007 Jarvis Moss was considered the top DE/OLB conversion prospect, and was a popular pre-draft pick for the Pats. Denver traded up to take him at #17, and was offering him for a 7th round pick during the last draft. We had just brought Adalius Thomas in as a FA, so going after Lamarr Woodley was never that likely. A lot of people thought we should have taken David Harris at #28, but BB didn't like the value and traded the pick, and we eventually ended up with a much better player. BB was also rumored to have targetted Stuart Bradley in the 3rd round, but Philadelphia took him at #87 right before we picked at #91, and we traded our pick away (for what we eventually traded up to get Ron Brace this year). Like Colvin, Thomas struggled a bit to pick up the system and didn't make quite as big a splash as envisioned in 2007.
The aging of the LB corps was obvious by the end of 2007, and BB reacted in the 2008 draft by bringing in not only Mayo but also Crable (the two highest drafted LBs in BB's tenure) as well as FA's Guyton and Redd, and 6th rounder Bo Ruud. A lot of people wanted Vernon Gholston, but he went #6, and did nothing. BB also brought in FA LB Victor Hobson who has been a 2nd round pick, but he was beaten out by Guyton and didn't make the squad.
So I don't think BB has exactly ignored the LB position. He has passed on some of my favorite prospects (Dansby, Barwin), but he has brought in 2 top FA LBs (Colvin and Thomas) and spent a high 1st and 3rd on the position recently. I think he just missed on 2 prospects who could easily have ended up Pats in Lofa Tatupa (at WILB) and Stuart Bradley (at SILB). And most of the top DE/OLB prospects were off the board long before the Pats have picked in most drafts.
As for the claims that Pittsburgh takes top LBs and is always loaded, I think those are also skewed. Joey Porter was a 3rd round pick in 1999, Clark Haggans a 5th rounder in 2000, Larry Foote a 4th rounder in 2002, and James Harrison an UDFA in 2002. The Steelers did take LBs in the 2nd round in 2001 (Kendrell Bell) and 2003 (Alonzo Jackson), but they didn't produce much. Pittsburgh took LBs at #15 and #46 in 2007; the Pats took LBs at #10 and #78 at 2008 (and they were going to take Crable at #69 before SD offered to trade their 2009 2nd round pick). Pittsburgh signed FA James Farrior, who was not considered an elite FA in 2002. The Pats signed FA LBs Roosevelt Colvin and Adalius Thomas, who were the top rated FA LBs in their respective years.
At this point BB has invested time and effort developing Pierre Woods (2006), Shawn Crable (2008), Vince Redd (2008) and Gary Guyton (2008). If he thinks they're worth continuing to develop, I don't see a problem with that.