Lightroom CC using a ton of extra space on hard drive. What went wrong?

I downloaded Lightroom CC. The migrate function did not work. Adobe support was not able to make it work after a 7 hours remotely driving my MacBook Pro. Finally, I imported all of my folders into Lightroom CC. I thought the whole idea was to keep files in the cloud to free up space on my computer. Now after 2 days of syncing, I have a massive "mobile downloads.lrdata" file in my boot drive and getting out of space messages. I used to have approx 9000 photos using Lightroom CC now Classic. Now I have over 12000. What went wrong. How do I fix this mess, please?