What would cause a sudden huge spike in crawling rate from google ??

So I have been checking my webmaster tools lately and in the crawl stats, there has been a very huge spike in crawl rates I noticed. My crawl rate per day was between 10,000 to 15,000 pages per day now it spiked to 150,000 per day 4 days ago , the day after that it was 170,000 pages per day .. now it spiked even more to 265,000 pages per day. At this pace, it may even start crawling a million page a day very soon.

I have to say that I'm quite happy to see such a huge spike but I'm wondering what caused it. I am suspecting that it may be due to the fact that I disavowed by really bad links a few days ago. I also did some changes to my site and my some of my urls changed structure. The thing is that I had done similar changes in the past but I never noticed such a huge spike. Maybe I did some things right this time. .. I really don't know. I was wondering if any of you had a similar experience.

I have been so busy with work that I kinda forgot to keep up with my SEO routine. Now I am back at it. Wanna take good care of this site and see where things go.