Without OSS we might have seen a more tepid period in the late 90s (smaller boom), as only those who could licenses IBM-whatever or MS-whatever webservers and DBs could make it to market. But also a correspondingly smaller bust, because only those with $$$$ would be able to make the investment, and due to the big barrier to entry likely would've won out their categories.
The fact that capabilities were open sourced confused the heck investors who'd been used to the MS/IBM world. They didn't understand how competition would work in the space. Hence terrible investment decisions that in retrospect look hilariously stupid.
Don't get me wrong: I much prefer the OSS world. But it's an instructive historical example. Today in AI, any old huckster with a naive nephew who knows how to finetuning things can come to market with something that looks magical to the folks holding the money bags, who likely can't differentiate between trivial hacks on top of open models and a deeper tech moat.