Trump was warned that the wheels of justice turns very very slowly but he mistook that as weakness because he is used to expediency. His presidency will be paralyzed as his close aides lawyer-up and start deserting him in fear of huge legal fees. Working for Trump is going to be very costly with a special prosecutor snooping around.
The way I see it, even if we argue that as of the day before the IC was named, Trump was as clean as pamba (not likely), his actions after that will constitute the offences that will bring him down.
I am not sure he understands the seriousness of "obstruction of Justice". Nixon was felled more by that than the actual burglaries. So was Bill Clinton.
I see Trump refusing to surrender documents and ordering the destruction of others. Like you say, legal fees can bankrupt a middle ranking mandarin who might also look at a long jail sentence. These will cut deals and spill the beans.