Briefly vs Simply - What's the difference?

In manner terms the difference between briefly and simply

is that briefly is in a brief manner, summarily while simply is weakly; foolishly; stupidly.

is that briefly is to be brief, in short while simply is frankly.

(en adverb)

(manner) In a brief manner, summarily.

He covered the subject briefly in his book.

(duration) For a brief period.

He only worked here briefly .

(speech act) To be brief, in short.

Briefly , I am not happy about what happened, but no one will be losing their job.

(en adverb)

(manner) In a simple way or state; considered in or by itself; without addition; alone.

(manner) Plainly; without art or subtlety; clearly; obviously; unquestionably.

(manner) Weakly; foolishly; stupidly.

(Johnson)

(focus) Merely; solely.

*{{quote-magazine, date=2013-06-01, volume=407, issue=8838

, page=13 (Technology Quarterly), magazine=(The Economist) , title= Ideas coming down the track , passage=A “moving platform” scheme

(degree) absolutely, positively.

(speech act) Frankly.

* complexly