I have read most of the lore of 4e, but never understood the need for a character that can do everything “magically”?
If you want to rig why not be a Rigger? Same with with hacking.
From various forums reactions to what happened to the archetype in 5e it sounded to me like their were too powerful to begin with.
Only when taken out of context. TMs were glass cannons, who were less effective in the meat world than a mundane hacker or rigger would be (because augmentations hurt their abilities). Because their Matrix condition track was their Brain, getting into matrix combat, any matrix combat, was dangerous. I like to compare them to D&D 3.X Wizards and Sorcerers. A 3.X Wizard has an insane number of things they can do, to the point where a prepared high level wizard who only has one fight that day is going to destroy pretty much anyone not made of antimagic fields, but they run out of gas quickly, due to limited spell slots. On the other hand, a Sorcerer has a more limited playbook, but they have more HP, can use their spells longer, and are generally more specialized. In this case, a Hacker would be like a Sorcerer, while a TM would be a Wizard. They are similar, but have different playstyles, different strengths and weaknesses.
The problem with 'arena' comparisons, which is what people did comparing a Hacker to a TM who threaded one obscenely powerful complex form were doing, is that what works in a single combat means crap all when you're on a 'dungeon run'. Because TMs were glass cannons, and were weaker than hackers in the meat (more attributes and skills to buy, buying their initial complex forms, not having augmentations, etc.), their weaknesses were more obvious once you were on the second or third encounter of a run, they took a hit in the meat which is hampering their Matrix stuff, and so on. When you're actually in play, TMs had better burst capabilities, and could adapt to new things better, but they were less resilient if you didn't give them time to sleep off their stun between encounters.
As for the 'need' for TMs? They were the spiritual successors to the Otaku of older years. And because a lot of people dig the technomystic, transhumanist streaks in the game, introduced in no small part by the otaku, and expanded upon by the growing forms and abilities of augmentations over the years, moving a cyberarm, for example, from 'necessary to replace a lost limb, and into 'voluntary upgrade' territory. Transhumanism, as in a desire to make oneself more than human, has been present throughout the game, to greater or lesser degrees, but as runners began shifting away from rabid neo-anarchists out to stick it to the man, and towards 'professional criminals that may or may not have agendas', that transhumanist element grew.