Mulitple BUF_X1 insertion in synthesized netlist

[ayewinoung]

I've synthesized netlist as below, I'm suprised to see so many buffers inserted by tool and using BUF_X1.
Can someone help me understand what parameters control how many buffers inserted and what type of buffer used ? e.g. why not use X4 and reduce the depth ? Is there some setting, I'm getting it wrong to output like this ? Thanks in advance.

Startpoint: 1874420 (rising edge-triggered flip-flop clocked by clk)
Endpoint: 1969079 (rising edge-triggered flip-flop clocked by clk)
Path Group: clk
Path Type: max

Delay Time Description

0.00 0.00 clock clk (rise edge)
0.00 0.00 clock network delay (ideal)
0.00 0.00 ^ 1874420/CK (DFF_X1)
0.08 0.08 v 1874420/Q (DFF_X1)
0.03 0.11 v 1655103/Z (BUF_X1)
0.23 0.34 ^ 1044126/ZN (NOR4_X1)
0.04 0.39 v 1044127/ZN (NAND2_X1)
0.15 0.54 ^ 1622690/ZN (NOR3_X1)
0.08 0.62 ^ 1623217/Z (BUF_X1)
0.08 0.70 ^ 1623743/Z (BUF_X1)
0.08 0.77 ^ 1623744/Z (BUF_X1)
0.07 0.85 ^ 1623907/Z (BUF_X1)
0.08 0.92 ^ 1624345/Z (BUF_X1)
0.08 1.00 ^ 1624981/Z (BUF_X1)
0.08 1.08 ^ 1624982/Z (BUF_X1)
0.08 1.15 ^ 1625321/Z (BUF_X1)
0.08 1.23 ^ 1625567/Z (BUF_X1)
0.08 1.30 ^ 1625568/Z (BUF_X1)
0.08 1.38 ^ 1625953/Z (BUF_X1)
0.08 1.46 ^ 1625954/Z (BUF_X1)
0.08 1.53 ^ 1626172/Z (BUF_X1)
0.08 1.61 ^ 1626446/Z (BUF_X1)
0.08 1.69 ^ 1626766/Z (BUF_X1)
0.08 1.76 ^ 1626948/Z (BUF_X1)
0.08 1.84 ^ 1626949/Z (BUF_X1)
0.08 1.91 ^ 1627080/Z (BUF_X1)
0.08 1.99 ^ 1627566/Z (BUF_X1)
0.08 2.07 ^ 1627567/Z (BUF_X1)
0.08 2.14 ^ 1627633/Z (BUF_X1)
0.02 2.17 v 1652619/ZN (AOI222_X1)
0.03 2.20 ^ 1652621/ZN (NAND3_X1)
0.02 2.22 v 1652622/ZN (XNOR2_X1)
0.03 2.25 ^ 1652623/ZN (OAI21_X1)
0.02 2.26 v 1652626/ZN (OAI21_X1)
0.08 2.34 ^ 1652627/ZN (NOR4_X1)
0.03 2.37 v 1652656/ZN (AOI22_X1)
0.03 2.40 v 1869924/Z (BUF_X1)
0.00 2.40 v 1969079/D (DFF_X1)
2.40 data arrival time

1.50 1.50 clock clk (rise edge)
0.00 1.50 clock network delay (ideal)
0.00 1.50 clock reconvergence pessimism
1.50 ^ 1969079/CK (DFF_X1)
-0.04 1.46 library setup time
1.46 data required time

       1.46   data required time
      -2.40   data arrival time

---

      -0.94   slack (VIOLATED)