AI agents like Alexa, Siri, and M will create the first trillion-dollar company

No, I don't think a chat assistant will be the first to reach and surpass $1 trillion. I think we are on the brink of something greater, with the confluence of AI, robotics and 3D printing.

I am thinking of an industrial process compiler that can plan and execute the multi-step process to create any object, using a combination of tools such as 3D printing, CNC-ing, assembling, casting, etc all from basic materials that are in abundance in nature.

If a complete database of industrial process knowledge would be coupled with a planning AI, and would be able to reproduce itself from raw materials as well as fulfilling all human needs, then sky is the limit. It would allow space colonization and an alternative to UBI.

Just ask your cousin to replicate a replicator for you. Then you would go home and download a car plan, customize it and have it compiled into physical form. Who needs UBI? You can print and assemble a robot to cultivate a small farm for your family and friends. This is the line of thinking that would lead to benefits in excess of what you can buy with $1 trillion, as long as a single replicator has been published in open source and physical form.

Some reading on this topic: https://en.wikibooks.org/wiki/Seed_Factories