The Bible can be read that God makes mistakes just as it can be read that people can change God's mind as happens repeatedly in the texts, but what some read that way, others read as all part of God's plan all along. People have wrestled with this for centuries. The Bible isn't univocal on pretty much anything like that and how culture views our relationship to the divine has altered so much it's hard to apply current ideas to it.
I'm sure we all agree that being transgender isn't a disease or a disaster? So I am wondering how it can be explained from a religious perspective.
Depends on how we define transgender.
Gender dysphoria, the distress at one's natural sex characteristics and being seen as that sex - some to the point of wanting to change their body (the vast majority do not), can feel like a disaster. That is a condition and some call that an essential part of being transgender.
People wanting to take on the roles of the other sex, that shows up in a lot of cultures, many without the body distress elements. Some also call that transgender, though there has been push back against that being applied to many groups - role-based is very different to identity/individualistic-based, which is why 'transgender and other gender diverse groups' is popping up in discussions on it. Role-based is not a condition, but personality within a culture that has strict defined roles, which often leads to more roles including cross-sex ones - societies like roles but people are complicated.
There are Judaic texts that have cross-sex role discussion, but they were not popular the variants that developed into Christianity and the Reformation pretty much moved religion from role-based to identity-based - that it's a natural internal drive to God that matters most. A lot of identity-based stuff in Western culture can be traced back to that major shift in how people framed their relationship and duties to the divine and others, and ultimately themselves.
That also means the texts were developed under role-based understanding, but identity-based is the basis for most doctrine and discussions on the Bible today. That clash is always going to be part of things like this. It's part of why the Calvinist and similar pre-determination doctrines gained ground, they blend both using texts like Romans 9 and those objects of wrath made for destruction to show God's glory to those he chooses to have mercy on (of course, to bring in Romans, we have to view Paul as an apostle rather than a false prophet Jesus warned about which is still an argument in some circles). It's not benevolent, not how most mean it today as it is a very selective kindness, but it blends the roles and identity-based concepts together in a way that's still in many doctrines.
I've at times viewed myself as an object of wrath and I've known others who've taken this route to this sort of question, but really, I just hold anything identity based very loosely with a text that wasn't written with that understanding to try to represent roles that have always been adapting - including the role of the Divine that's any text (let alone one translated from copies, some we can see were altered to try to create more consensus that still doesn't exist) can only be an incomplete representation of an attempt of trying to define and understand.
I don't see chronic illness and disability as the same as neurodiversity.
Depends on how we define neurodiversity. Some only use it to mean autism (as it's origin with an autistic sociologist) and ADHD, but it's widely used to include other ways the brain works differently from 'standard' such as Dyslexia, Dyscalculia, Dyspraxia, Tourettes and Tic disorders, FASD (considered the most common preventable intellectual disability), and acquired neurodiversities like traumatic brain injuries, post-stroke, and similar.
There have been arguments within each of these, like all groups, but all of them have discussed the need for disability-related accomodations and FASD in particularly have been very vocal about being equally a disability and neurodivergent and that taking the disability out is harmful and while benefits to using the social model, it would still be disabling. Few things are universally agreed to be strengths, and there are risks to using them to outweigh everything else.