I can understand why in the context of today's discussions on gender, and I see a need for it, but what were the main reasons for creating iĉismo? I would like to know who created it and why.
The default for certain core words is masculine. You can explicitly call out anything as feminine with -in-. This leads some people rather directly to thinking of an entity in any role as masculine unless it's explicitly called out. Conversely, it makes it difficult to specify that a person is male.
In real life, men are not the default, and women are not aberrations from the default. Both are equal options. We want a language that reflects that.
The Fundamento endorses ge- as a prefix to be used for groups of mixed gender. In other words, if you see doktorojn kaj doktorinojn, you can say that you saw gedoktorojn. If you need to go to see a doctor, you need to see a doktoron aŭ doktorinon, or unu de la gedoktoroj, or you can merely hope that your audience doesn't think you are speaking specifically about male doctors.
By reinterpreting all words as not specifying a gender and adding an explicit masculine affix that parallels the feminine affix, we fix this problem.
However, there is a large body of work with slightly conflicting usage. While this shift doesn't invalidate most usages of the masculine-or-epicene, it does invalidate some of them. This is a barrier to adoption.
Furthermore, since the rationale is to resolve a gender issue, a lot of people jump out of the woodwork to defend the status quo. They will say that any sexism is in the mind of the speaker, not in the language. That might be true, but in this case, the language certainly isn't helping, and that makes the language less useful for communication -- which is the entire reason it was built. But regardless, this is still a barrier to adoption.
My understanding is that iĉismo is a lighter form of riismo, which has been around at least since the early 90's. Here is an early description viewable via the "Wayback Machine."
There's a lot of information there. I thought this part was particularly relevant to your question:
Pro la evidenta analogeco "panjo - patrino : paĉjo - patriĉo" la sufikso -iĉ- estas multfoje kaj sendepende inventita de multaj diversaj homoj. Verŝajne ankaŭ la pronomo ri havas multajn inventintojn; se oni metas vokalon I post ĉiu konsonanto kaj forstrekas la radikojn, kiuj estas jam uzataj aŭ kiuj tro similas al alia pronomo, kiun oni intencas daŭre uzi, restas nur malmultaj ebloj.
When Esperanto was created, animate roots that referred to people or animals were almost completely male or female. Unmarked roots were male and had to be marked to be female (koko "rooster", kokino "chicken"), or they were inherently female and weren't marked to be masculine as their meaning inherently referred to women (ex. damo "lady/queen", nimfo "nymph"), as is the case in the majority of European languages. As time progressed the majority of inherently male roots became gender neutral. This led to the desire to fully neutralize the remaining masculine roots (patro "father", reĝo "king") and itroduce a masculine suffix similar to -ino so that Esperanto would be completely neutral.
When it comes to movements like these, it is not always a single person who leads it. Even if a manifesto is written and the followers of the idea have a name for themselves (as is the case with riismo), this does not necessarily mean that they will have a leader or named founders. Often with affairs like these, a group of people may spread the idea anonymously, or people or groups of people may independently develop the concept and spread it anonymously. As to who created iĉismo, the best answer is that we don't know and that we may never know.
PS: This is a subjective evaluation of the situation, but if their anonymity is intentional, they may have desired that we more so consider whether or not their proposal has merit compared to other proposals, as opposed to the celebrity of Zamenhof and Sonja Lang if the affair succeeds, or the infamy of Louis de Beaufront if it failed.