In solar the answer is easy. Companies in the sector (Oriana, Bondada, Insolation) have delievered explosive growth in topline & earnings, with strong future visibility. So market ready to pay in anticipation for any new company, until they disappoint.
Other sectors are an extension of this to some extent though only a handful sectors trade at 70+ pe (power / transmission, defense, ems). This party will last till the next earnings cycle that disappoints (as long as liquidity & policy remain conducive). When that will happen is anyones guess.
@Unknown Man