Why discrease the domain authority amount?

[SamA74]

Probably due to spammy links you create, such as the one I just removed from your post here.

Also note the comments in this recent topic:-

@juuneedvoila

Moz recently introduces DA 2.0 Update because of this update many websites lose DA just because of spammy backlinks. Now Moz also considering Quality backlinks rather than quantity of backlinks. My site also hit and some it’s DA and PA decrease a little bit after Moz update but we don’t have to take DA seriously.
Domain Authority for a Domain - #3 by juuneedvoila