Problem with chain skipping when pedaling hard
Since the rings, cogs and chain are new, and decent components we can safely eliminate the possibility that there is a problem with the chain grabbing the rings or cogs.

Here is what I suspect might be happening: it's your derailleur: due to wear, damage or perhaps weakened springs.

Here is how: as you pedal, the chain temporarily catches in the derailleur cage. The next thing that happens is that, since the chain is not moving through the derailleur, the entire derailleur is pulled by the chain and rotated backwards, which basically peels/unwraps the chain from the cassette until it loses grip.

You only notice this when there is significant load on the chain, like going uphill. Under light load, you just need one or two teeth of grip, if the chain and cassette are new.

There is no substitute for having someone watch what is going on. Or attaching a camera to a chain stay or seat stay to record what is going on.

If the derailleur is the culprit, you probably wasted money on the new crankset. Two-year old rings are probably still okay, and in any case, individual rings can be replaced, not the entire crankset.