my last ticket for my home match was sold out but after the game it was only 729 people i had as attendance instead of 1500 which is my stadium capacity since all my ticket were sold out
can someone explain why it like that to me

Popularity (yours and your opponent's) determines your home match attendance, not necessarily the amount of tickets you sold. Sure, those tickets do work towards your popularity. But, just because you sold all tickets, that doesn't mean you should expect your stadium to be full.

It's explained here (although not terribly well):

https://rockingsoccer.com/en/soccer/help/home/category-10/article-24

Essentially each time someone clicks on your link and buys tickets you sell "books" of tickets. At stadium level 2 you sell 15 tickets at a time.

A maximum of 10 people can buy your tickets for each match, so being "sold out" only means you have sold 10 lots of 15 tickets which is 150. 

Your attendance will be 150 plus whatever you get from your popularity. You also get an extra 10 for every manager that watches your game.

okay
so how can i boost my attendance then??

You can build the office to put a staff member to increase attendance. Also if you watch the matches live you get 20% more attendance. 

These are the two ways to increase the team's popularity and the attendance. 

what about fanshop
is that not supposed to boost attendance ??

Office will help you put staff member to your other facilities.

Yes fanshop increase your popularity.. 

The most important ways to boost your attendance is actively selling your tickets for your match, build your fanshop, put staff member to it, watch your match live to get 20% attendance bonus.

The fanshop increases your attendances, but only indirectly.

The purpose of the fanshop is to gradually build your popularity over time. More popularity means higher attendances. A higher level fanshop will see your popularity increase more quickly. 

Bulding your popularity is the main key to growing the club as it will provide most of your future income.  

Popularity >>> Attendances >>> Build higher level stadium >>> More income

Fanshop increases popularity, but it also helps to boost your attendance.  More popularity, more attendance.

To increases your attendance you need to put a staff member in the stadium. That's why I was talking about the office.

https://rockingsoccer.com/es/futbol/help/home/category-16/article-76