In many cases interceptions are dependent on the opponents offense making a mistake. The QB throws a ball and doesn't see the defender lurking nearby or under/over throws the pass. Sometimes a reciever slips and falls. Sure the defense also gets some of the credit for interceptions and I don't mean to make out like they're just benefitting from blind luck or anything like that.
When you see the Texans giving up 3rd down conversion after 3rd down conversion this is indicative of what they are. This is showing you the lack of consistency that they're sufferring from. Ending drives in turnovers is a good thing but most teams (particularly most good teams) aren't going to give you a mistake you can exploit for a turnover on most drives.
The Texans need to stop more drives by forcing punts. The turnovers are nice, great even, but they've got to be able to lock a team down and keep them from getting that next ten yards if they want to win games.