As my favorite dance teacher always says.. Getting to the top is easy. Staying there is hard. Trying to inbox emails, is exactly the same.
Your ability to get more email opens and Inbox is based on your Email Reputation. The same way that Facebook Ads give you relevance score based on your targeting and engagement.
Just remember Email Reputation changes daily, sometimes hourly and having a having a the right hygiene process in place, is your #1 step to trying to get more email opens and clicks.