I think a large part of its valuation was it's ability to compete with search but thats understating it a bit. Unlike search it could/can be the platform users primarily interact with (ala a social media replacement) while having huge impacts on enterprise work and automation. I think its the combination of the ability for effectively one company to compete on every front in the modern web ecosystem thats contributed to the valuation.

It's also important to note the valuation is not just based off of its possible concrete economic implications in these areas but also future "unknown" possibility ( I.E. whatever "agi" means to investors ). Thats not to say I believe it's possible to achieve this but rather a huge part of Sam Altman's job is increasing valuation through unfounded claims of AGI's possibility and possible impact.