Would it be possible to overtake the network by running a secluded mining operation for many years? I have a scenario. Let's say I start my own Bitcoin mining on a secluded network. I leave this to mine for many years or even pass it down to future generations.

To the very point that my chain is longer than the worlds current chain. Then I connect to the network. What would the result be? Would I instantly own every coin mined?
'Longer' means 'more total work spent'. You're not going to be working harder than all miners put together are you? Then the only way to get some money is to join the existing miners and work with them. And by doing that you coincidentally enlarge the group of 'honest' miners, making it that much harder for someone else to consider your  'evil' plan.