As other people have said... Size and athletic ability are #1.

But don't overlook drive and mental determination (at #2)... if your kid doesn't have the mental strength to use #1 and do EVERYTHING required it won't happen.

#3 is money.. It costs a truck-load-of-cash in today's world to get a kid into D1 (unless #1 puts you at the 5* level, which is very-very-very rare.. and still won't happen without #2)

#4 is connections (and sometimes luck). Your kid needs to be on the right teams and get in front of the right people.

#5 is a parent willing to put in the work. I've seen tons of kids with #1 and #2 but their parents have the attitude "if it's something he wants, he'll make it happen". Times have changed... and if your kid isn't that 0.001% 'special' athlete it requires a crap-ton of work from a parent. All to often you see parents of kids entering JR year of HS sports asking "What do I need to do to get my kid recruited". The sad answer is: Should have been working on that in middle school.

For background.. I have one son who played D1 football and made it into the NFL. I have another son who is currently playing D1 football.

I also have a 7'1" nephew who had #1, didn't get #2 until his sr year of HS, but his parents had #3-#5. He was lucky to walk on at a Juco in basketball and got a few D2 offers and one or two D1 walk-on offers this year. But probably will do another year of Juco to try for better D1 options. If he had put more effort into the sport in Jr High and high school... He wouldn't be driving for DoorDash right now.

I've also seen far too many kids make it into D1 and quit because it's harder than they expected. Lots of kids are big and athletic, but not a lot of kids have the mental strength to cope with the demands (abusive coaches, abusive fans, wear and tear on the body, and knowing that every year the coaches have signed a kid to take your spot).