A proper coup looks like this: sneak overwhelming force into the capital somehow, shoot the first few people who dare to resist, and let everyone else get the message that you're the new sheriff in town. Kill the incumbents, if they have an independent power base. Capture them, if you were the power base.
History has plenty of examples of people who rose in armed rebellion against a lawful government, like this. That's a little more chancy.
Every dictator has powerful political opponents. Going about this war in the way that he did, which cost the oligarchs that propped him up a great deal of money, made him a lot more internal enemies with some clout than before.
@trueblue84 Putin's position is indeed very precarious, now. The military is the kingmaker, and Putin is also dependent upon the Chinese for financing.