That is natural enough.

For Browning's dramas were written when he was young, when his knowledge of the dramatic art was small, and when his intellectual powers were not fully developed.
Tennyson wrote his when his knowledge of the Drama was great, and when his intellect had undergone years of careful training.

He studied the composition and architecture of the best plays; he worked at the stage situations; he created a blank verse for his plays quite different from that he used in his poems, and a disagreeable thing it is; he introduced songs, like Shakespeare, at happy moments; he imitated the old work, and at the same time strove hard to make his own original.

He laboured at the history, and _Becket_ and _Harold_ are painfully historical.

History should not master a play, but the play the history.