Here's a clue, Mr. President---they did warn people about him. Again and again. You might care to ask @mystery-ak 's question---who dropped the balls?
Mueller/Comey/Wray's FBI dropped the ball.
These career govt. LEO hacks aren't really that good. By that I mean the entire organization, top to bottom. Somebody is establishing priorities, and setting limits for how much to pursue certain leads.
--Sept. 11 "on their radar"
--Boston Marathon "on their radar"
--Ft. Hood "on their radar"
--San Bernardino "on their radar"
--Orlando FL "on their radar"