Orbital data centers are impractical for a lot of reasons (to put it mildly) but radiation shielding isn’t one of them. Proportionally less shielding is needed as one scales up, due to lower surface/volume ratios.
There are ways in which shielding in space can do harm: really energetic particles get trapped and produce a shower of daughter particles and rays over a greater area. So you'd need even more shielding. Or you accept that such things will happen and use rad-hard parts, redundancy etc. When you have the whole atmosphere above, it's much less of a concern.
Besides, that's even more mass to be lofted. Pushing the economics further into the ludicrous end.