THE FLT CREW ENCTRD SVR TURBC IN CRUISE FLT AT FL410, OVER A VIP LVL 4 TO 5 THUNDERSTORM. THE #2 ENG FLAMED OUT, THOUGH CONTINUOUS IGNITION HAD BEEN SELECTED. AFTER THE FLAME-OUT, THE ACFT STARTED TO DSCND & THE CREW BGN TO DIVERT TO A NRBY ARPT. DRG THE DSCNT, THE ACFT ENCTRD LARGE HAIL, HVY RAIN, SVR TURBC, LIGHTNING & ST ELMOS FIRE. THE OTR ENG FLAMED OUT AS THE ACFT WAS DSCNDG THRU FL330 (PRESUMABLY DUE TO HAIL & WATER INGESTION). ATTEMPTED AIR STARTS (BOTH WINDMILLING & STARTER ASSISTED) WERE UNSUCCESSFUL; INTERIOR LGTS BCM EXTREMELY DIM DRG STARTER ASSISTED ATMTS. SUBSEQUENTLY, THE ACFT WAS DMGD DRG A LNDG IN A WHEAT FLD. INV REVEALED THE CREW DID NOT RCV A WX BRIEFING BFR THE FLT. THERE WAS A CONVECTIVE SIGMET (6C) & AN ALERT WX WARNING (AWW 163), WHICH WERE ACTIVE FOR THE AREA. ACCORDING TO A WX STUDY, THERE WAS A SVR THUNDERSTORM, TOPPED AT OR NR FL410, MDT TO SVR UP/DWNDFTS, LARGE HAIL, HVY RAIN, STRONG WIND GUSTS, AND AIRFRAME ICING ABV 12,000' MSL. ALL FRONTAL AREAS OF THE ACFT RCVD MDT TO SVR HAIL DMG.