Why do car issues happen all at once

Just a frustration post. Yesterday I took my Mustang to mechanic to get some electrical issues diagnosed so the dash is currently torn apart in the shop. Cool. No problem, I'll just drive the truck like I have been dd for the past 3-4 months.Then when trying to leave for work today my truck decides to crank no start... just my damn luck. Both vehicles have well over 230k on the clock so I guess I shouldn't be too shocked lol