The big assumption is that "the largest shareholders are absolutely for this". I don't think this is necessarily the case. Minds change all the time. (Note: I think most of the largest shareholders were for it earlier on but later filings showed a lot of what I call the "dismalness of SCTY" and that's changing people's minds.)
If the largest shareholders were truly absolutely for this, then this would cause no stress on Elon as it would be a done deal. But obviously (as evidenced by Elon's own words this past Sunday), it's causing him a lot of stress due to the flak and it shows that there are a lot of significant institutional investors who are against this deal or are becoming increasingly belligerent toward the deal's prospects.
Another factor is look at the SCTY's share price... If TSLA's at $200, SCTY should be at $22 (due to the 0.11 stock swap offer by TSLA). But it's significantly lower. Why? Investors on the Street are well connected and the stock is $17 (and not $22) because of two reasons:
1. SCTY's finances are dismal (and most of that info was disclosed after TSLA's initial offer, thus the drop after).
2. There's a high risk of SCTY bankruptcy if the deal doesn't go through (due to SCTY finances being so dismal).
3. There's a decent chance the deal doesn't go through. If the deal was 99% going through, then there wouldn't be such a large difference ($17 vs $22), as institutions would be buying up SCTY to get a huge discount on TSLA. But big institutions/funds are well-connected and they recognize there's a good chance (ie., 20-50%???) that the deal won't go through.
I regretfully feel the same way.