When USAAF heavy bombers started appearing they caused problems for the Luftwaffe's fighter force, whose armaments at the time could not adequately destroy B-17s and B-24s deployed in the combat box formation. And fighter escort usage meant the earlier solution using Bf110 bomber destroyers was no longer viable.
So the decision was made to modify the rugged Focke Wulf 190 into a bomber interceptor, modifying it with heavier armaments including 30mm cannons and unguided rockets plus heavy armor; but these rendered the planes cumbersome and useless without fighter escort.
