There are times when the place to be is in mega-caps.

Though true, I think it would be fruitful to refine that:

There are times when the place to be is in certain specific individual firms that are doing particularly well, or are seen to be doing particularly well.
Sometimes those few are, more or less by coincidence, extremely large firms.
At those times (and in general only those times) a cap weight approach does particularly well versus any other diversified investing approach.

The justifiable portion of the observation that this has been the place to be lately is primarily down to the vagaries of the specific firms, not down to the specific fact that those firms are huge. Sometimes all the very best performing firms have tickers starting with the letter A, and that's the place to be. It isn't a rule you can generalize, though.

Why split hairs?
I think it's important to make the distinction in this particular case because the general long run rule in the past appears not to have been random chance, but the reverse. Very frequently (but not always) the very largest cap firms achieve that crown via material overvaluation which doesn't last, leading to poor forward returns. Among the 500 largest stocks by market cap, the CAGR of the top 7 (equally weighted) has been more than 2%/year lower than the CAGR of the next 493 in the last 38 years, a stretch which includes the recent FAANG+ leadership.

Jim