Is it bad practice to submit the entire manuscript for an initial book proposal to a publisher?
Did you follow the book proposal guidelines for Springer? It does not include sending the entire manuscript but does include items like:


Author
Author CV
Any other contributors (include CVs)? 
Who's the audience including undergraduate or graduate 
What book do you see as the main competitor? 
3-4 paragraphs describing the contents of the book 
Unique Selling Points (why should someone buy this book)
etc.


Note: I'm not sure that I've linked to the book proposal guidelines for your area, but they surely exist.

Second Note: Geremia provided a link to the book series webpage. Poking around on the page and tracing links, I did find a general manuscript preparation page, but nothing on what the proposal should look like. I maintain that unless they tell you explicitly to send the entire manuscript, you should send a brief proposal or even a query ("are there guidelines I should follow?") to the editor first. 

Based on blogs and articles that I've read by fiction editors and agents, not following published guidelines for a submission is one of the top pet peeves and a quick way for your submission to get deleted or tossed in the recycle bin.