> I went through two iterations of reaching out to my college network. The first time I put so much time into handwriting notes and trying to provide my relatable background. 100 notes, not a single response.
This is a thoughtful gesture, but there are at least two problems with it
First, a handwritten note isn't easy to respond to. With an e-mail, you can leave the message in your inbox until you have time to respond and then it's one click to start responding. With a hand-written letter the recipient would have to context-switch from reading mail to using a digital device and they'd have to transcribe your e-mail address. It's not much work, but it's still work that someone has to make time for.
Second, it's an unusual thing to do. It's important to communicate with people through normal, comfortable communication channels where the etiquette is known. Having someone handwrite a letter and look up your mailing address is unusual. Unusual behavior triggers people's suspicions. You weren't trying to scam anyone, but you should be aware that one of the tricks used in scams is to invest unusual amounts of attention and energy into someone. It can trigger a suspicion that you're really after something else.
Your second round of sending short e-mails had neither of these problems. Easy to reply to, nothing unusual about it. It's the way to go.