If you had been able to choose Python/Backbone etc. in the big company, chances are that it would have taken even longer. In big companies, everything is different, and they have to take other things in regard than mere development time. They are most likely prepared for one or two kinds of tech stacks, and everything is in place for that. If suddenly they have to deploy new technology, they for example have to:
* build custom monitoring for the components in the new stack
* look at support contracts and patching procedures for these components
* figure out how to be able to respond to security incidents with these new components
* train and _keep_ training people specifically for this new special snowflake you just created for the years to come
* look into how various operational concerns are implemented with this technology: scaling, separation of concerns (can I deploy the admin part separately?), logging and log rotation, and so forth
In startups, developer cost and time to market may be the most important things. In bigger companies, a lot of other things start to matter.
* build custom monitoring for the components in the new stack
* look at support contracts and patching procedures for these components
* figure out how to be able to respond to security incidents with these new components
* train and _keep_ training people specifically for this new special snowflake you just created for the years to come
* look into how various operational concerns are implemented with this technology: scaling, separation of concerns (can I deploy the admin part separately?), logging and log rotation, and so forth
In startups, developer cost and time to market may be the most important things. In bigger companies, a lot of other things start to matter.