Why would someone “less smart” not deserve success?

Being smart helps a lot in life, and in many paths of life is key. However:

• It is not the only thing you need. Life requires resilience, perseverance, work, etc, just to exist.
• Intelligence is a skill. You can become more intelligent.
• Perceived skills not necessarily align with actual skills.
• You do not need to be the best, just good enough to achieve objectives without harming your fellow humans.
• Sometimes you aren’t in the right place at the right time. That’s just luck.

You seem to be suffering from imposter syndrome. Step 1 is to understand that we’re all just winging it.

Are you getting the job done? Plenty of people you perceive as smarter than you are not getting the job done.