I suspect even just loaning powerful people money at that time was effectively being on them / a political act in the first place. Less so that it built up over time and surprised anyone.
This is true to some extent, but his debtors had a strong interest in Julius Caesar's continued success--which means that even if his later actions were ones that the debtors would not have supported originally, their wagons had been hitched to his and they had a very strong incentive to support him.