I don't think the big companies will do any damage for bitcoin. It's not in their interest. Although they can undoubtedly drop the price for a while to get a chance to buy cheap coins. But now that they are here, they undoubtedly have a strong interest in bitcoin to make a profit. So in the future the prices will be much higher than they are now.
I wish you were right, but I share the opinion of some other people who think that BTC ETFs are very likely to cause a lot more problems than good. I've already posted that link on the forum several times, so even though it's about posts from 5 years ago, I think that what @theymos wrote definitely makes sense - although it would be interesting to know if he still thinks the same today.
You must know that the interest of big companies is exclusively profit, and that they do not choose ways to achieve the same. But most of these companies just use everything they can and then move on, and I think that Bitcoin is no exception to that.
Agreed, an ETF will almost certainly turn into a disaster at some point. The coins will be stolen, forks will be handled controversially, there will be issues with fungibility (eg. someone will "trace stolen coins" to the ETF's stash), the world will freak out when a bunch of retirees lose their life savings after doing the equivalent of buying BTC at $20k, etc. etc. It'll also get the sort of people who love regulation more into BTC, which is never good.
But investors want it, so it'll probably happen eventually. In particular, I totally condemn trying to get regulators to interfere in the free market more than they already do by blocking any ETF. (When the SEC was last looking into this, I had actually written a long document that I was going to send to them in order to comment on many technical issues with their proposed Bitcoin ETF regulation, but I decided not to send it because I don't want to have even the slightest hand in regulations.)
An ETF probably will increase the price a lot (until the ETF suffers its near-inevitable catastrophe), which has some pros and cons.
Note that an ETF can't affect Bitcoin itself, just the ETF investors and the market. There is no voting of any sort in Bitcoin, so it's not as if holding a lot of BTC gives you any power over Bitcoin, for example. I do agree with Andreas that the creation of a "corpo-Bitcoin" seems probable, perhaps after the ETF loses a ton of BTC and wants to undo it.