It’s been done many times.

Some examples: https://www.dragonflytelescope.org/gallery.html is an array of telescopes (long off the shelf photographic lenses) to achieve exactly that. Photographic lenses tend to give higher image quality, but don’t gather enough light. Solution? Stack many of them and point in the same direction. It’s not just a flight of fancy, they made some breakthrough science with this.

A somewhat less relevant case is ALMA - millimetre wave array in the Atacama. Millimetre waves are a bit longer than IR, somewhat between IR and microwave, and telescopes look like radio dishes, not optical devices. Anyway, the array stacks many tens of such receivers to produce one antenna with a massive effective diameter. In this case, the key advantage is in fact resolution: by spreading the dishes around, you get much higher overall resolution than one massive dish, something we probably couldn’t achieve with IR (too computationally expensive).

Whether launching 10 satellites with 1/3 mirror diameter is cheaper is a whole different question.

Not sure why you're bringing land based solutions to the conversation with "it's been done many times".

If that's the case Webb has been done many times and is super easy.

The physics of stacking detectors doesn't depend on space vs. land. 100 "blunt" telescopes does give you a "sharp" one, on Earth and in orbit.

It does when the position of each sensor relative to the position of the others matters. On earth that's trivial, but if you're 1.5 million kms out in space you could imagine this being significantly more difficult.

Not to mention, each of these 100 units would require the same shielding from radiation as the giant one does for the same reasons. We chose L2 for a very good reason; where are these 100 going to go? What are the odds that each one will end up where it needs to be x100 attempts?