During the 70s and into the early 80s, C compilers were relatively easy to come by for personal computers, although most only did a subset of C (which is why you'll see so many different "tiny C" compilers adverts in the older magazines). Pascal was a larger more cumbersome language back in the days when only the wealthiest computer hobbyists had hard drives (and a 5 meg hard drive was several hundred dollars). For the Apple 2 (my first computer, and it wasn't even a "plus"), running Pascal required purchasing an extra memory card (it needed 64k of RAM!) and took several floppies to load up, while "tiny C" compilers fit on a single floppy (and could get by with 16k of RAM).
Pascal was taught in computer science curricula, while C was mostly self-taught (sometimes taught in electrical engineering curricula). Pascal got a reputation among the cowboy coders for being a "bondage and discipline language", which I thought was undeserved as they never met ADA.
The major drivers of Pascal in the 80s were Apple (because the APIs used Pascal calling standards) and Borland. Borland's "Turbo" compilers were probably the best available ones in the marketplace, and the "like a book" license made them a lot more popular than companies with more vicious licensing.
Borland lost their lead in the development market when Microsoft hired away their lead developers and project managers (such as Hejlsberg, Gross and more than 35 others), eventually developing .NET and Visual Studio. Borland and Microsoft settled the lawsuit a couple years later, but Borland never recovered from the loss. In my opinion, Delphi started withering at that time (as the folks who gave it focus and drive were hired away), and the change in CEO at the same time took Borland away from a compiler company into an ALM (application lifecycle management) company, changing their name to Inprise a couple years later. The ashes of Borland are now owned by Micro Focus.