Neither did Vue, or Django, or Rails or dozens of other successful and widely adopted technologies. Svelte's issue is probably that it came out a little too lat

Neither did Vue, or Django, or Rails or dozens of other successful and widely adopted technologies. Svelte's issue is probably that it came out a little too late: companies have adopted React, Vue or Angular, and have sufficient inertia (existing codebases and hard-won experience) that there is little incentive to switch just for a slightly nicer syntax or state management model.