We actually started out in 2019 by colocating our own network/server equipment in a colo facility in Frankfurt (InterXion). We are bootstrapped and since our USP is the software, not the infrastructure, we decided to partner with a reliable infrastructure company that is available globally, flexible enough and for data privacy reasons is an EU based company (there are not many!) so we could roll out our platform faster. Since we still own our own IP space and are a RIPE member, we can migrate to our own infrastructure down the road.
In this business the focus shouldn't be to own the whole "supply chain", but to deliver a reliable solution to customers. Everyone is a reseller of someone.
Nodion -> Leaseweb. Leaseweb -> Iron Mountain. Iron Mountain -> electricity companies, dark fiber, etc.
Heroku/Vercel -> AWS. AWS also uses colo facilities like Equinix, InterXion, NTT or e-shelter in Frankfurt.