"でltあ" or simply "≜"(U+225C) is an internet slang meaning "it was supposed/meant to be blah blah blah".
"でltあ" is an output when you
key-in "delta" on Japanese FTPs for "≜ (delta equal to)" to emphasize "by
definition" while it looks like "でしたぁ" (lt. 'was/were' but the last letter ぁ implicits 'sorry to say, but actually...' like 'umm...' in
American)