I think you're just misunderstanding the notion of 0. Now and in the past, 0 interest in TSLA meant they didn't own TSLA. It's too hard. These people are very conservative, low risk. If you're benchmarked against an index with no TSLA then there's no point in fooling around with TSLA.
I think you're misunderstanding what benchmarked against means.
It means they want to
beat the results of the index.
Why would you mirror something you are trying to do better than?
They held 0 TSLA because they felt it would not help them BEAT the index results.
If a managed fund that charges significant fees were to report "Hey we exactly matched the returns o a passive S&P index fund!" their customers would wonder WTF they're spending their money on with those fees.
Buying into stocks NOT in the index is
literally the only way to beat it
But as soon as the benchmark buys TSLA, then the new 0 is owning exactly the same percentage. So if you are a conservative, low risk fund manager then you buy TSLA to be equal weight with the benchmark, and since it's too hard you never think about it again.
Again- how does that make any sense?
At that point they're just a passive index fund- not an actively managed fund trying to
beat the index.
If you want to BEAT the index, mirroring it is exactly the way to insure you fail at your one job.
So pre-inclusion, an active fund manager either thought TSLA would do worse than the index as a whole, and bought 0.
Or she thought it would beat the index as a whole and bought shares (see ARK as the most obvious example of such a fund).
The same is true post inclusion.