What were the motivations for Sri Lanka's banning of chemical fertilizers?

Sri Lanka is going through a serious crisis caused by a number of economic factors. One recurring theme, besides the Covid tourism crash, is the collapse of local agriculture following a ban on industrial fertilizers (or at least on importing them) in favor of all-organic fertilizers.

Googling the terms fertilizer sri lanka why quickly shows all sorts of issues with the implementation of this policy. From deficient Chinese imports to farmer productivity crashes.

But why was that ban implemented in the first place?

• what did the government's declarations of intent during its election campaigning cite as reasons?

• what have opposition politicians/media cited as possible motivations?

(Sri Lanka ranks 146/180 on Reporters wo Borders Press Freedom index in 2022, so be mindful of that when citing local newspapers like this article.)

p.s. Spelling out the obvious: this is not asking multiple questions in asking what the govt said or what the opposition said. Citing those possible sources is to pre-empt the other close vote reason: Questions asking for the internal motivations of people, .... So what did either source have to say?